radeonsi: don't leave more than 8 unoccupied lanes in HS

Previously it was 16 and bigger patches would always trim the patch count
needlessly.

There are 2 variables to consider:
- lane occupancy
- LDS usage (limiting wave occupancy)

If LDS size is 32 KB (max limit per CU) for 3 waves and we can't maximize
occupancy, it's better to leave some lanes unoccupied because using 2
waves would decrease the LDS size to 21 KB, which is not enough to fit
another workgroup on the CU.

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7623>

src/gallium/drivers/radeonsi/si_state_draw.c

@@ -176,7 +176,8 @@ static void si_emit_derived_tess_state(struct si_context *sctx, const struct pip
    unsigned temp_verts_per_tg = *num_patches * max_verts_per_patch;
    unsigned wave_size = sctx->screen->ge_wave_size;
 
-   if (temp_verts_per_tg > wave_size && temp_verts_per_tg % wave_size < wave_size * 3 / 4)
+   if (temp_verts_per_tg > wave_size &&
+       (wave_size - temp_verts_per_tg % wave_size >= MAX2(max_verts_per_patch, 8)))
       *num_patches = (temp_verts_per_tg & ~(wave_size - 1)) / max_verts_per_patch;
 
    if (sctx->chip_class == GFX6) {