panfrost: Stop using panfrost_emit_for_draw() for compute jobs

panfrost: Stop using panfrost_emit_for_draw() for compute jobs

We actually need a small subset of what's done in
panfrost_emit_for_draw() when emitting compute jobs, so let's copy
what we need directly in panfrost_launch_grid() instead of re-using
this function whose initial purpose was to generate vertex/tiler jobs
for draw operations.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4083>