panfrost: Keep track of active BOs

panfrost: Keep track of active BOs

If two jobs use the same GEM object at the same time, the job that
finishes first will (previous to this commit) close the GEM object, even
if there's a job still referencing it.

To prevent this, have all jobs use the same panfrost_bo for a given GEM
object, so it's only closed once the last job is done with it.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Rohan Garg <rohan.garg@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>