The e500mc does not actually support the mfocrf instruction; update the
processor definitions to reflect that fact.
Patch by Tom Rix (with some test-case cleanup by me).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254064 91177308-0d34-0410-b5e6-96231b3b80d8
