[MachineScheduler] checkResourceLimit boundary condition update

When we call checkResourceLimit in bumpCycle or bumpNode, and we
know the resource count has just reached the limit (the equations
 are equal). We should return true to mark that we are resource
limited for next schedule, or else we might continue to schedule
in favor of latency for 1 more schedule and create a schedule that
 actually overbook the resource.

When we call checkResourceLimit to estimate the resource limite before
scheduling, we don't need to return true even if the equations are
equal, as it shouldn't limit the schedule for it .

Differential Revision: https://reviews.llvm.org/D62345

llvm-svn: 362805