[X86] Remove isel patterns for MOVSS/MOVSD ISD opcodes with integer types.

Ideally our ISD node types going into the isel table would have types consistent with their instruction domain. This prevents us having to duplicate patterns with different types for the same instruction.

Unfortunately, it seems our shuffle combining is currently relying on this a little remove some bitcasts. This seems to enable some switching between shufps and shufd. Hopefully there's some way we can address this in the combining.

Differential Revision: https://reviews.llvm.org/D49280

llvm-svn: 337590