[AMDGPU] Do not apply schedule metric for regions with spilling

D139710 has added a metric to increase schedule's ILP while
staying within the same occupancy. Do not bother to apply this
metric to a region which is known to have spilling, it may result
in spilling to reappear after the previous stage and will do no
good if we already spilling anyway. It may also reduce compile
time a bit for such regions.

Fixes: SWDEV-377300

Differential Revision: https://reviews.llvm.org/D143934