[X86][SkylakeServer] Remove checks for 'k', 'z', '_Int' and 'b' from scheduler regexs.

Most of these were optional matches at the end of the strings, but since the strings themselves are prefix matches by default you don't need to check for something optional at the end.

I've left the 'b' on memory instructions where it means 'broadcast' because I'm not sure those really have the same load latency and we may need to split them explicitly in the future.

llvm-svn: 328730