drm/bridge: panel: Remove a redundant check on existence of bridge->encoder

Because the existence of 'bridge->encoder' has already been checked before
the panel_bridge_attach() function get called, and the drm_bridge_attach()
will quit with a negative error code returned if it fails for some reasons.
Hence, it is guaranteed that the .encoder member of the drm_bridge instance
is not NULL when panel_bridge_attach() function get called.

Remove the redundant checking codes "if (!bridge->encoder) { ... }".
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240513153109.46786-5-sui.jingfeng@linux.dev

drivers/gpu/drm/bridge/panel.c

@@ -67,11 +67,6 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
 	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
 		return 0;
 
-	if (!bridge->encoder) {
-		DRM_ERROR("Missing encoder\n");
-		return -ENODEV;
-	}
-
 	drm_connector_helper_add(connector,
 				 &panel_bridge_connector_helper_funcs);