Mips: Make test resistant to future changes

This seems to have been relying on extra spills being inserted in
these blocks to increase the code size to trigger branch
relaxation. This broke when these spills were avoided. Add some asm to
pad the size of the blocks to make it not matter.

llvm/test/CodeGen/Mips/branch-relaxation-with-hazard.ll

@@ -38,11 +38,13 @@ entry:
   br i1 %cmp, label %if.then, label %if.end4
 
 if.then:
+  call void asm sideeffect ".space 10", "~{$1}"()
   %1 = load i32, i32* %argc.addr, align 4
   %cmp1 = icmp sgt i32 %1, 3
   br i1 %cmp1, label %if.then2, label %if.end
 
 if.then2:
+  call void asm sideeffect ".space 10", "~{$1}"()
   %call = call i32 bitcast (i32 (...)* @boo to i32 ()*)()
   store i32 %call, i32* %retval, align 4
   br label %return