[X86] Fix a bug in LOCK arithmetic operation pattern matching where the wrong...

[X86] Fix a bug in LOCK arithmetic operation pattern matching where the wrong immediate predicate check was being used for 64-bit instructions with 8-bit immediates.

This didn't cause a bug because the order of the patterns ensured that the 64-bit instructions with 32-bit immediates were selected first.

llvm-svn: 268212