drm/connector: Clarify when drm_connector_unregister is needed

The current documentation for drm_connector_unregister() mentions that
it's needed for connectors that have been registered through
drm_dev_register().

However, this was a typo and was meant to be drm_connector_register(),
which only applies to connectors registered after drm_dev_register() has
been called.

In addition, it was also mentioning that connectors are unregistered
automatically when drm_dev_unregister() is called. This part is a bit
misleading, since it might make it appear that
drm_connector_unregister() applies either to all connectors, or none of
them.

After discussing it with Daniel, it appears that we always need to call
drm_connector_unregister() on connectors that have been registered with
drm_connector_register(), but only those.

drm_connector_init() already mentions that it only needs
drm_connector_cleanup(), so let's clarify the drm_connector_register()
and drm_connector_unregister() documentation to point at each other, and
remove the misleading part about drm_dev_unregister().
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220711173939.1132294-7-maxime@cerno.tech

drivers/gpu/drm/drm_connector.c

@@ -525,6 +525,9 @@ EXPORT_SYMBOL(drm_connector_cleanup);
  * e.g. DP MST connectors. All other connectors will be registered automatically
  * when calling drm_dev_register().
  *
+ * When the connector is no longer available, callers must call
+ * drm_connector_unregister().
+ *
  * Returns:
  * Zero on success, error code on failure.
  */
@@ -581,9 +584,8 @@ EXPORT_SYMBOL(drm_connector_register);
  * @connector: the connector to unregister
  *
  * Unregister userspace interfaces for a connector. Only call this for
- * connectors which have registered explicitly by calling drm_dev_register(),
- * since connectors are unregistered automatically when drm_dev_unregister() is
- * called.
+ * connectors which have been registered explicitly by calling
+ * drm_connector_register().
  */
 void drm_connector_unregister(struct drm_connector *connector)
 {