[X86][AVX512F] minor fix of the parameter names

add "__" prefix

Bug 28842 https://llvm.org/bugs/show_bug.cgi?id=29040

Differential Revision: https://reviews.llvm.org/D23753


 


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@279392 91177308-0d34-0410-b5e6-96231b3b80d8