media: amphion: Fix race between m2m job_abort and device_run

Fix kernel panic caused by race condition where v4l2_m2m_ctx_release()
frees m2m_ctx while v4l2_m2m_try_run() is about to call device_run
with the same context.

Race sequence:
v4l2_m2m_try_run(): v4l2_m2m_ctx_release():
lock/unlock v4l2_m2m_cancel_job()
job_abort()
v4l2_m2m_job_finish()
kfree(m2m_ctx) <- frees ctx
device_run() <- use-after-free crash at 0x538

Crash trace:
Unable to handle kernel read from unreadable memory at virtual address
0000000000000538
v4l2_m2m_try_run+0x78/0x138
v4l2_m2m_device_run_work+0x14/0x20

The amphion vpu driver does not rely on the m2m framework's device_run
callback to perform encode/decode operations.

Fix the race by preventing m2m framework job scheduling entirely:
- Add job_ready callback returning 0 (no jobs ready for m2m framework)
- Remove job_abort callback to avoid the race condition

Fixes: 3cd084519c6f ("media: amphion: add vpu v4l2 m2m support")
Cc: stable@vger.kernel.org
Signed-off-by: Ming Qian <ming.qian@oss.nxp.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>