[X86] Use the same predicate for the load for PMOVSXBQ and PMOVZXBQ.

These both use a 16-bit load, but one used loadi16_anyext and the other used extloadi32i16. The only difference between them is that loadi16_anyext checked that the load was at least 2 byte aligned and non-volatile. But the alignment doesn't matter here. Just use extloadi32i16 for both.

llvm-svn: 329154