Adjust MachineScheduler to use ProcResource counts

This fix allows the scheduler to take into account the number of instances of
each ProcResource specified. Previously a declaration in a scheduler of
ProcResource<1> would be treated identically to a declaration of
ProcResource<2>. Now the hazard recognizer would report a hazard only after all
of the resource instances are busy.

Patch by Jackson Woodruff and Momchil Velikov.

Differential Revision: https://reviews.llvm.org/D51160

llvm-svn: 360441