[X86] For AVX1/AVX2 isel, don't use FP move instructions for 128-bit loads/stores of integer types.

For SSE we use fp because of the smaller encoding, but that doesn't apply to AVX. So just do the natural thing so we don't have to explain why we aren't. We can't do this for 256-bit loads/stores since integer loads and stores aren't available in AVX1 so we need fallback patterns since the integer types are legal.

This doesn't affect any tests because execution domain fixing freely converts the instructions anyway. Honestly, we could probably rely on it for the SSE size optimization too.

llvm-svn: 293743