drm/client: Export drm_client_dev_unregister()

drm/client: Export drm_client_dev_unregister()

Export drm_client_dev_unregister() for use by the i915 driver. The
driver does not use drm_dev_unregister(), so it has to clean up the
in-kernel DRM clients by itself.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240409081029.17843-2-tzimmermann@suse.de
Signed-off-by: Jani Nikula <jani.nikula@intel.com>