Fix assert when encoding stdbrx

When encoding the stdbrx instruction we hit the following assert:

```
Instruction 0xffef3295360 [stdbrx] (generated from node 0xffef30913b0 [lstorei]): Format 0 cannot be binary encoded by PPCMemSrc1Instruction

Instruction context:

...
     0xfff6c0b9a98 000000a8 [     0xffef3294e80] 7cc0e808          85 	twlle 	gr0, gr29
     0xfff6c0b9a9c 000000ac [     0xffef3294f90] 387d0007          86 	addi 	gr3, gr29, 7
     0xfff6c0b9aa0 000000b0 [     0xffef3295030] 7cc01808          85 	twlle 	gr0, gr3
     0xfff6c0b9aa4 000000b4 [     0xffef32951b0] 7fa307b4          86 	extsw 	gr3, gr29
     0xfff6c0b9aa8 000000b8 [     0xffef32952c0] 38630008          88 	addi 	gr3, gr3, 8
 [     0xffef3295360]	88 	stdbrx 	[gr3, gr27], gr26		# SymRef  <generic int shadow>[#492  Shadow] [flags 0x603 0x0 ]
 [     0xffef3295400]	88 	fence 	Relative[ f3050434 ] (BBEnd (block_7))
 [     0xffef3295ef0]	88 	assocreg
 PRE:
POST: [GPR_     0xffef3293780 : gr26] [&GPR_     0xffef32936d0 : gr27] [GPR_     0xffef3293620 : gr28] [GPR_     0xffef3293570 : gr29]
 [     0xffef3295fb0]	91 	fence 	Relative[ f3050560 ] (BBStart (block_8))
 [     0xffef3296040]	91 	Label [     0xffef3293350]:
 [     0xffef32960d0]	91 	ret
...
(Set env var TR_AssertFullContext for full context)

Node context:

...
n115n     lstorei  <generic int shadow>[#492  Shadow] [flags 0x603 0x0 ] ()                   [     0xffef30913b0] bci=[-1,88,322] rc=0 vc=837 vn=- li=7 udi=- nc=2 flg=0x20
n956n       aladd (X>=0 internalPtr sharedMemory )                                            [     0xffef31e1a90] bci=[-1,85,322] rc=0 vc=837 vn=- li=7 udi=- nc=2 flg=0x8100
n982n         ==>aRegLoad
n955n         lsub (highWordZero X>=0 cannotOverflow )                                        [     0xffef31e1a40] bci=[-1,88,322] rc=0 vc=837 vn=- li=7 udi=- nc=2 flg=0x5100
n954n           i2l (highWordZero X>=0 )                                                      [     0xffef31e19f0] bci=[-1,86,322] rc=0 vc=837 vn=- li=7 udi=- nc=1 flg=0x4100
n980n             ==>iRegLoad
n953n           lconst -8 (X!=0 X<=0 )                                                        [     0xffef31e19a0] bci=[-1,88,322] rc=0 vc=837 vn=- li=7 udi=- nc=0 flg=0x204
n952n       lbyteswap                                                                         [     0xffef31e1950] bci=[-1,84,322] rc=1 vc=837 vn=- li=7 udi=- nc=1
n983n         ==>lRegLoad
...
```

The problem seems to be because the format is not specified for this
instruction.

Signed-off-by: Filip Jeremic <fjeremic@ca.ibm.com>

compiler/p/codegen/OMRInstOpCodeProperties.hpp

@@ -4770,7 +4770,7 @@
    /* .description =    "Store doubleword byte reverse indexed", */
    /* .prefix      = */ 0x00000000,
    /* .opcode      = */ 0x7C000528,
-   /* .format      = */ FORMAT_UNKNOWN,
+   /* .format      = */ FORMAT_RS_RA_RB_MEM,
    /* .minimumALS  = */ OMR_PROCESSOR_PPC_P7,
    /* .properties  = */ PPCOpProp_IsStore |
                         PPCOpProp_ExcludeR0ForRA,

fvtest/compilerunittest/p/BinaryEncoder.cpp

@@ -4355,6 +4355,10 @@ INSTANTIATE_TEST_CASE_P(StoreIndex, PPCMemSrc1EncodingTest, ::testing::ValuesIn(
     std::make_tuple(TR::InstOpCode::stwbrx,  MemoryReference(TR::RealRegister::gr31, TR::RealRegister::gr0 ), TR::RealRegister::gr0,   0x7c1f052cu, false),
     std::make_tuple(TR::InstOpCode::stwbrx,  MemoryReference(TR::RealRegister::gr0,  TR::RealRegister::gr31), TR::RealRegister::gr0,   0x7c00fd2cu, false),
     std::make_tuple(TR::InstOpCode::stwbrx,  MemoryReference(TR::RealRegister::gr0,  TR::RealRegister::gr0 ), TR::RealRegister::gr31,  0x7fe0052cu, false),
+    std::make_tuple(TR::InstOpCode::stdbrx,  MemoryReference(TR::RealRegister::gr0,  TR::RealRegister::gr0 ), TR::RealRegister::gr0,   0x7c000528u, false),
+    std::make_tuple(TR::InstOpCode::stdbrx,  MemoryReference(TR::RealRegister::gr31, TR::RealRegister::gr0 ), TR::RealRegister::gr0,   0x7c1f0528u, false),
+    std::make_tuple(TR::InstOpCode::stdbrx,  MemoryReference(TR::RealRegister::gr0,  TR::RealRegister::gr31), TR::RealRegister::gr0,   0x7c00fd28u, false),
+    std::make_tuple(TR::InstOpCode::stdbrx,  MemoryReference(TR::RealRegister::gr0,  TR::RealRegister::gr0 ), TR::RealRegister::gr31,  0x7fe00528u, false),
     std::make_tuple(TR::InstOpCode::stwcx_r, MemoryReference(TR::RealRegister::gr0,  TR::RealRegister::gr0 ), TR::RealRegister::gr0,   0x7c00012du, false),
     std::make_tuple(TR::InstOpCode::stwcx_r, MemoryReference(TR::RealRegister::gr31, TR::RealRegister::gr0 ), TR::RealRegister::gr0,   0x7c1f012du, false),
     std::make_tuple(TR::InstOpCode::stwcx_r, MemoryReference(TR::RealRegister::gr0,  TR::RealRegister::gr31), TR::RealRegister::gr0,   0x7c00f92du, false),
@@ -4413,6 +4417,7 @@ INSTANTIATE_TEST_CASE_P(StoreIndex, PPCRecordFormSanityTest, ::testing::Values(
     std::make_tuple(TR::InstOpCode::stvehx,  TR::InstOpCode::bad,     BinaryInstruction()),
     std::make_tuple(TR::InstOpCode::stvewx,  TR::InstOpCode::bad,     BinaryInstruction()),
     std::make_tuple(TR::InstOpCode::stwbrx,  TR::InstOpCode::bad,     BinaryInstruction()),
+    std::make_tuple(TR::InstOpCode::stdbrx,  TR::InstOpCode::bad,     BinaryInstruction()),
     std::make_tuple(TR::InstOpCode::bad,     TR::InstOpCode::stwcx_r, BinaryInstruction()),
     std::make_tuple(TR::InstOpCode::stwux,   TR::InstOpCode::bad,     BinaryInstruction()),
     std::make_tuple(TR::InstOpCode::stwx,    TR::InstOpCode::bad,     BinaryInstruction()),