[llvm][MIRVRegNamerUtils] Adding hashing on FrameIndex MachineOperands.

This patch makes it so that cases where multiple instructions that differ only
in their FrameIndex MachineOperand values no longer collide. For instance:

%1:_(p0) = G_FRAME_INDEX %stack.0
%2:_(p0) = G_FRAME_INDEX %stack.1

Prior to this patch these instructions would collide together.

Differential Revision: https://reviews.llvm.org/D71583