radeonsi: Process multiple patches per threadgroup.

radeonsi: Process multiple patches per threadgroup.

Using more than 1 wave per threadgroup does increase performance
generally.  Not using too many patches per threadgroup also
increases performance. Both catalyst and amdgpu-pro seem to
use 40 patches as their maximum, but I haven't really seen
any performance increase from limiting the number of patches
to 40 instead of 64.

Note that the trick where we overlap the input and output LDS
does not work anymore as the insertion of the tess factors
changes the patch stride.

v2: - Add comment about LDS assumptions.
    - Add constant for buffer size.
    - Fix code style.

v3: - Correct limits for not splitting patches between waves.
    - Set max num_patches to 40 as in the proprietary driver.

Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>