Kernel is a port of `ggml-cuda/fwht.cu`
(us/run, median):
```
m x n x k GEMM FWHT speedup
64 x 1 x 64 10.20 2.93 3.48x
64 x 2048 x 64 10.75 2.71 3.97x
128 x 1 x 128 10.33 2.88 3.59x
128 x 32 x 128 9.20 2.77 3.33x
128 x 2048 x 128 16.46 2.76 5.95x
256 x 1 x 256 10.19 2.77 3.68x
256 x 2048 x 256 16.69 3.41 4.89x
512 x 2048 x 512 54.16 12.89 4.20x
```
Titaniumtown
0882c7bc89