[MIPS] Fix a incorrect test. (NFC)

This test is incorrect as it should be using the microMIPSR6 instruction to
return, not the microMIPS version.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354726 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed