Rename mattr names for AVX-512 to from avx-512 -> avx512f, avx-512-pfi -> av512pf, avx-512-cdi -> avx512cd, avx-512-eri->avx512er. This matches better with official docs and what gcc patches appearto be using. I didn't touch the has* functions or the feature flag names to avoid change the td and lowering file while commits are still happening.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188859 91177308-0d34-0410-b5e6-96231b3b80d8