drm/v3d: Use scheduler dependency handling

With the prep work out of the way this isn't tricky anymore.

Aside: The chaining of the various jobs is a bit awkward, with the
possibility of failure in bad places. I think with the
drm_sched_job_init/arm split and maybe preloading the
job->dependencies xarray this should be fixable.

v2: Rebase over renamed function names for adding dependencies.

Reviewed-by: Melissa Wen <mwen@igalia.com> (v1)
Acked-by: Emma Anholt <emma@anholt.net>
Cc: Melissa Wen <melissa.srw@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Emma Anholt <emma@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210805104705.862416-11-daniel.vetter@ffwll.ch