media: bcm2835-unicam: Fix a NULL vs IS_ERR() check

The media_pad_remote_pad_unique() function returns error pointers, not
NULL. Update the check accordingly.

Fixes: 392cd78d495f ("media: bcm2835-unicam: Add support for CCP2/CSI2 camera interface")
Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Laurent Pinchart <[e-mail]>

drivers/media/platform/broadcom/bcm2835-unicam.c

···
 		return ret;
 
 	source = media_pad_remote_pad_unique(sink);
-	if (!source) {
+	if (IS_ERR(source)) {
 		dev_err(unicam->dev, "No connected sensor pad\n");
-		return -ENOTCONN;
+		return PTR_ERR(source);
 	}
 
 	unicam->sensor.subdev = subdev;