[X86][IR] In AutoUpgrade, check explicitly for xop.vpcmov and xop.vpcmov.256...

[X86][IR] In AutoUpgrade, check explicitly for xop.vpcmov and xop.vpcmov.256 instead of anything starting with xop.vpcmov

There were some older intrinsics that only existed for less than a month in 2012 that still exist in some out of tree test files that start with this string, but aren't able to be handled by the current upgrade code and fire an assert. Now we'll go back to treating them as not intrinsics at all and just passing them through to output.

Fixes PR32041, sort of.

llvm-svn: 295930