[X86] Remove some check-prefixes from avx512-cvt.ll to prepare for an upcoming patch.
[X86] Remove some check-prefixes from avx512-cvt.ll to prepare for an upcoming patch.

The update script sometimes has trouble when there are check-prefixes representing every possible combination of feature flags. I have a patch where the update script was generating something that didn't pass lit.

This patch just removes some check-prefixes and expands out some of the checks to workaround this.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@324819 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm