gallium: add indirect compute parameters to pipe_grid_info

gallium: add indirect compute parameters to pipe_grid_info

Like indirect draw, we need to store a resource and an offset that
needs to be 4 byte aligned. When indirect is used, the size of the
grid (in blocks) is stored with three 32-bit integers.

Changes from v2:
 - s/most values/block sizes/

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>