drm/bridge: imx8qxp-ldb: Fix NULL pointer dereference in imx8qxp_ldb_bridge_destroy()

Pointer bridge->driver_private in imx8qxp_ldb_bridge_destroy() is NULL
when a LDB channel is unavailable or imx8qxp_ldb_probe() returns error,
because ldb_add_bridge_helper() is the last function called from
imx8qxp_ldb_probe() and it doesn't initialize bridge->driver_private if
a LDB channel is unavailable.  The NULL pointer would be set to pointer
ldb_ch and then NULL pointer ldb_ch would be dereferenced.  Fix this
by returning early from imx8qxp_ldb_bridge_destroy() if !ldb_ch is true.

Fixes: 32529d3 ("drm/bridge: imx8qxp-ldb: convert to of_drm_find_and_get_bridge()")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260123-imx8qxp-drm-bridge-fixes-v1-1-8bb85ada5866@nxp.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Author: Liu Ying

drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c

@@ -65,9 +65,12 @@ static inline struct imx8qxp_ldb *base_to_imx8qxp_ldb(struct ldb *base)
 static void imx8qxp_ldb_bridge_destroy(struct drm_bridge *bridge)
 {
 	struct ldb_channel *ldb_ch = bridge->driver_private;
-	struct ldb *ldb = ldb_ch->ldb;
-	struct imx8qxp_ldb *imx8qxp_ldb = base_to_imx8qxp_ldb(ldb);
+	struct imx8qxp_ldb *imx8qxp_ldb;
+
+	if (!ldb_ch)
+		return;
 
+	imx8qxp_ldb = base_to_imx8qxp_ldb(ldb_ch->ldb);
 	drm_bridge_put(imx8qxp_ldb->companion);
 }