CUDA: mul_mat_id for mmf for bs <= 64 for f16 and bs <= 32 for f32 (llama/16277)

CUDA: mul_mat_id for mmf for bs <= 64 for f16 and bs <= 32 for f32 (llama/16277)

* CUDA: mul_mat_id for mmf for bs <= 64 for f16 and bs <= 32 for f32

This commit adds mul_mat_id support for ncols_dst >= 16. It does this by
packing ncols_dst tiles into the blockDim.y.

My tests on a RTX 3090 show that this is faster than the cuBLAS fallback
for f16 till bs=64, and for f32 till bs=32

* Review: refactor if statement