drm/log: Do not hold lock across drm_client_release()

When calling drm_client_release(), the client is already quiescent.
Internal locks should therefore be dropped before the caller releases
the client.

In the case of the DRM log, concurrency originates from the console or
from client events. The console has been unregistered in the previous
line. The caller of the unregister callback, drm_log_client_unregister(),
holds clientlist_mutex from struct drm_device to protect against concurrent
client events. It is therefore safe to release the client without holding
locks.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>>
Link: https://lore.kernel.org/r/20251009132006.45834-3-tzimmermann@suse.de