radeonsi: bump SI_NUM_SHADER_BUFFERS to 32

radeonsi: bump SI_NUM_SHADER_BUFFERS to 32

Some app uses more than 8 SSBOs (https://gitlab.freedesktop.org/mesa/mesa/-/issues/2946),
so increase SI_NUM_SHADER_BUFFERS to 32 (which allows 16 SSBOs).

Since we're now using a 64 bits number to track buffers, we could bump
SI_NUM_SHADER_BUFFERS to 48 but that would conflict with Mesa's
MAX_COMBINED_ATOMIC_BUFFERS limit (= 90).

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2122
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5632>