* q2_k_r4: Zen4
PP-512(LLaMA-3.1-8B) = 256 t/s
* q3_k_r4: AVX2
* q2_k_r4: AVX2
We get PP-512(LLaMA-3.1-8B) = 287 t/s.
Also cherry-picked the q3_k_r4 AVX2 adaptation that I somehow
forgot to push upstream.
* q2_k_r4: NEON
We get PP-512(LLaMA-3.1-8B) = 106.2 t/s.
TG-128 is 36.02 t/s, which is ~10% higher than q2_K_S.
* Make sure rows per thread are a multiple of 4
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Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>
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