[X86] Skip (v2i32/v4i16/v8i8 (bitcast (f64))) handling in ReplaceNodeResults...

[X86] Skip (v2i32/v4i16/v8i8 (bitcast (f64))) handling in ReplaceNodeResults if the dest type can be widened by generic legalization. NFCI

The algorithm we would do previously was identical to generic legalization. If we ever switch to legalizing integer vectors via widening we'll be able to kill off the code since it now only runs for promotion.

llvm-svn: 344423