drm/panfrost: Display list of device JM contexts over debugfs

drm/panfrost: Display list of device JM contexts over debugfs

For DebugFS builds, create a filesystem knob that, for every single open
file of the Panfrost DRM device, shows its command name information and
PID (when applicable), and all of its existing JM contexts.

For every context, show the DRM scheduler priority value of all of its
scheduling entities.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20250917191859.500279-5-adrian.larumbe@collabora.com