gallium/util: Fix location of the comment about S8_UINT handling.

I clearly wrote it in the wrong place in "softpipe: Refactor
pipe_get/put_tile_rgba_* paths."

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5728>
1 file changed