amd/common: move ac_memory_ops_per_clock into shared header

This is (originally) a part of !17331 (merged), with slight edits to have a more generic naming. I'll update that MR once this one is merged.

I decided to move this particular change to a separate MR because it would also be used in a Radeon Raytracing Analyzer tracing utility (which I'm currently working on). Merging this change beforehand allows me to open a separate MR for RRA support when I finished implementing it, and not having to wait until !17331 (merged) is merged.