[llvm] AMDGPU: Correct cycle counts for f64 mfma on gfx940 (PR #83782)

[Matt Arsenault via llvm-commits]

arsenm wrote:

>  The code related to 8 pass DGEMM now needs to be moved from 'case 16' to 'case 8' in the 
> `GCNHazardRecognizer::checkMAIVALUHazards`.

This one avoids the test changes

> `GCNHazardRecognizer::checkMAIHazards90A` 

This one seems to be unnecessary since it's special casing the MFMA_F64 opcodes before that switch 


https://github.com/llvm/llvm-project/pull/83782