musa: restore MUSA graph settings in CMakeLists.txt

[yeahdongcn]

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Testing Done

root@7bd6a1e5dcc0:/ws# cmake -B build -DGGML_MUSA=ON -DMUSA_ARCHITECTURES=21 -DGGML_CUDA_GRAPHS=ON
root@7bd6a1e5dcc0:/ws# cmake --build build -j 16 --config Release

[JohannesGaessler]

(If you get the CI to work.)

[yeahdongcn]

(If you get the CI to work.)

Thanks for the review! No problem — I’ll fix the CI.

Just a heads-up: we're preparing a new MUSA SDK release, which includes some API naming changes. Unfortunately, I haven’t found a clean way to maintain compatibility across versions yet. I’ll coordinate with the team to determine the best practice for handling this.