vulkan: matmul gcn tuning (#13016)
* tune matmul for gcn
* this one is more power efficient
* Update ggml/src/ggml-vulkan/ggml-vulkan.cpp
Co-authored-by: 0cc4m <picard12@live.de>
* disable this tune for the proprietary driver
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Co-authored-by: 0cc4m <picard12@live.de>
