drm/bridge: waveshare-dsi: Fix bailout for devm_drm_bridge_alloc()

devm_drm_bridge_alloc() returns ERR_PTR on failure instead of a
NULL pointer, so use IS_ERR() to check the returned pointer and
turn proper error code on failure by using PTR_ERR().

Fixes: dbdea37 ("drm: bridge: Add waveshare DSI2DPI unit driver")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250806084121.510207-1-victor.liu@nxp.com

Author: Liu Ying

drivers/gpu/drm/bridge/waveshare-dsi.c

@@ -147,8 +147,8 @@ static int ws_bridge_probe(struct i2c_client *i2c)
 	int ret;
 
 	ws = devm_drm_bridge_alloc(dev, struct ws_bridge, bridge, &ws_bridge_bridge_funcs);
-	if (!ws)
-		return -ENOMEM;
+	if (IS_ERR(ws))
+		return PTR_ERR(ws);
 
 	ws->dev = dev;