[X86] Change the signature of the AVX512 packed fp compare intrinsics to...

[X86] Change the signature of the AVX512 packed fp compare intrinsics to return vXi1 mask. Make bitcasts to scalar explicit in IR

Summary: This is the clang equivalent of r324827

Reviewers: zvi, delena, RKSimon, spatel

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D43143

llvm-svn: 324828