fast: add fused_swiglu_gather_qmv (Metal kernel fusing SwiGLU + gather_qmm)#2

benjamin-levin merged 5 commits into

mainbenjamin-levin/mlx:mainfrom

fused-swiglu-gather-qmv-prbenjamin-levin/mlx:fused-swiglu-gather-qmv-prCopy head branch name to clipboard