CUDA: Remove unneded bias/gate dims in fused mmvq (llama/16858)

CUDA: Remove unneded bias/gate dims in fused mmvq (llama/16858)

* CUDA: Remove unneded bias/gate dims in fused mmvq

Pointed out
[here](https://github.com/ggml-org/llama.cpp/pull/16847#discussion_r2476798989)
that only a single value is needed per target col per thread

* Apply suggestions from code review

Co-authored-by: Johannes Gäßler <redacted>
* Fix "Error 991-D: extra braces are nonstandard" during compilation

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Co-authored-by: Johannes Gäßler <redacted>