[llvm] [AMDGPU] Add stalls for DS FIFO buffer to coexec sched (PR #185726)

[Lucas Ramirez via llvm-commits]

https://github.com/lucas-rami commented:

Just did an initial pass on `AMDGPUCoExecSchedStrategy.h`, will continue later on the rest.

https://github.com/llvm/llvm-project/pull/185726