[X86] Use native shuffle vector for the perm2f128 intrinsics

This patch replaces the perm2f128 intrinsics with native shuffle vectors.

This uses a pretty simple approach to allocate source 0 to the lower half input and source 1 to the upper half input. Then its just a matter of filling in the indices to use either the lower or upper half of that specific source. This can result in the same source being used by both operands. InstCombine or SelectionDAGBuilder should be able to clean that up.

Differential Revision: https://reviews.llvm.org/D37892

llvm-svn: 313418