ggml-cpu: Optimized x86 and generic cpu q1_0 dot (follow up) (#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