ggml-cpu: Optimized x86 and generic cpu q1_0 dot (follow up) (llama/21636)

ggml-cpu: Optimized x86 and generic cpu q1_0 dot (follow up) (llama/21636)

* Implemented optimized q1_0 dot for x86 and generic

* Removed redundant helper definition

* Removed two redundant instructions from AVX q1_0 dot

* Fixed inconsistency with fp16 conversion for generic q1_0 dot and deduplicated generic fallback

* Style cleanup around AVX q1_0 dot

* Replaced explicitly unrolled blocks with inner for loop for q1_0

* Replaced scalar ARM q1_0 impl with new generic one