Change when SupportsAlignedAccessOnly flag is set

SupportsAlignedAccessOnly flag is no longer set for 64 bit Power 9.
SupportsAlignedAccessOnly flag is no longer set for 64 bit BE Power 8.
SupportsAlignedAccessOnly flag is now set for 32 bit Power 7.

This is done to more accurately represent which cases have performance
issues with unaligned accesses.

Signed-off-by: jimmyk <jimmyk@ca.ibm.com>

compiler/p/codegen/OMRCodeGenerator.cpp

@@ -278,10 +278,11 @@ OMR::Power::CodeGenerator::initialize()
    if (cg->is64BitProcessor())
       cg->setSupportsInlinedAtomicLongVolatiles();
 
-   // Standard allows only offset multiple of 4
-   // TODO: either improves the query to be size-based or gets the offset into a register
-   if (comp->target().is64Bit())
+   if (!comp->target().cpu.isAtLeast(OMR_PROCESSOR_PPC_P9) &&
+       !(comp->target().cpu.isBigEndian() && comp->target().cpu.is(OMR_PROCESSOR_PPC_P8)))
+      {
       cg->setSupportsAlignedAccessOnly();
+      }
 
    // TODO: distinguishing among OOO and non-OOO implementations
    if (comp->target().isSMP())