drm/connector: Add drm_connector_find_by_fwnode() function (v3)

[ Upstream commit 3d3f7c1e68691574c1d87cd0f9f2348323bc0199 ]

Add a function to find a connector based on a fwnode.

This will be used by the new drm_connector_oob_hotplug_event()
function which is added by the next patch in this patch-set.

Changes in v2:
- Complete rewrite to use a global connector list in drm_connector.c
  rather then using a class-dev-iter in drm_sysfs.c

Changes in v3:
- Add forward declaration for struct fwnode_handle to drm_crtc_internal.h
  (fixes warning reported by kernel test robot <lkp@intel.com>)

Tested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20210817215201.795062-4-hdegoede@redhat.com
Stable-dep-of: 89434b069e46 ("usb: typec: altmodes/displayport: Signal hpd low when exiting mode")
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/drm/drm_connector.h

@@ -1193,6 +1193,14 @@ struct drm_connector {
 	 */
 	struct list_head head;
 
+	/**
+	 * @global_connector_list_entry:
+	 *
+	 * Connector entry in the global connector-list, used by
+	 * drm_connector_find_by_fwnode().
+	 */
+	struct list_head global_connector_list_entry;
+
 	/** @base: base KMS object */
 	struct drm_mode_object base;