[MCSchedule] Always generate processor resource names.

With this patch, the tablegen 'SubtargetEmitter' always generates processor
resource names. 
The impact of this patch on the code size of other llvm tools is small.  I have
observed an average increase of 0.03% in code size when doing a release build of
LLVM (on windows, using MSVC) with all the default backends.

This change is done in preparation for the upcoming llvm-mca patch.

llvm-svn: 326993