ggml: aarch64: Implement SVE in Gemm q4_k 8x8 q8_k Kernel (#19132)
* Updated repack.cpp
* Updated repack.cpp
* Updated repack.cpp
* Added if condition to support only vector length 256.
* Changed the format removed comments and duplicate variable
* If SVE 256 not present then was using generic function to compute, hence slowing the performance.
So added code if SVE 256 is not present then use NEON code.
* Code format change suggestion
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Co-authored-by: Vithule, Prashant <Prashant.Vithule@fujitsu.com>