[X86] Don't allow lods/stos/scas/cmps/movs to be parsed without a suffix and...

[X86] Don't allow lods/stos/scas/cmps/movs to be parsed without a suffix and only memory operand in at&t syntax.

Without a register with a size being mentioned the instruction is ambiguous in at&t syntax. With Intel syntax the memory operation caries a size that can be used to disambiguate.

llvm-svn: 322356