drm/panfrost: use scheduler dependency tracking

Just deletes some code that's now more shared.

Note that thanks to the split into drm_sched_job_init/arm we can now
easily pull the _init() part from under the submission lock way ahead
where we're adding the sync file in-fences as dependencies.

v2: Correctly clean up the partially set up job, now that job_init()
and job_arm() are apart (Emma).

v3: Rebased over renamed functions for adding depdencies

Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Acked-by: Emma Anholt <emma@anholt.net>
Reviewed-by: Steven Price <steven.price@arm.com> (v3)
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: Emma Anholt <emma@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210805104705.862416-8-daniel.vetter@ffwll.ch