[X86] Add 512-bit unmasked pmulhrsw/pmulhw/pmulhuw intrinsics. Remove and auto...

[X86] Add 512-bit unmasked pmulhrsw/pmulhw/pmulhuw intrinsics. Remove and auto upgrade 128/256/512 bit masked pmulhrsw/pmulhw/pmulhuw intrinsics.

The 128 and 256 bit versions were already not used by clang. This adds an equivalent unmasked 512 bit version. Then autoupgrades all sizes to use unmasked intrinsics plus select.

llvm-svn: 325559