[AMDGPU] Add s_nop WaitStates between neighboring mfma

In some cases padding bubbles between sequential MFMA instructions may
lead to increased inter-wave performance. Add option to request to pad
some portion of these stall cycles with s_nops.

Fixes: SWDEV-326925

Reviewed By: rampitec

Differential Revision: https://reviews.llvm.org/D121437