mailbox: Use dev_err when there is error

Use dev_err to show the error log instead of using dev_dbg.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

Author: MrVan

drivers/mailbox/mailbox.c

@@ -322,7 +322,7 @@ static int __mbox_bind_client(struct mbox_chan *chan, struct mbox_client *cl)
 	int ret;
 
 	if (chan->cl || !try_module_get(chan->mbox->dev->driver->owner)) {
-		dev_dbg(dev, "%s: mailbox not free\n", __func__);
+		dev_err(dev, "%s: mailbox not free\n", __func__);
 		return -EBUSY;
 	}
 
@@ -413,7 +413,7 @@ struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
 	ret = of_parse_phandle_with_args(dev->of_node, "mboxes", "#mbox-cells",
 					 index, &spec);
 	if (ret) {
-		dev_dbg(dev, "%s: can't parse \"mboxes\" property\n", __func__);
+		dev_err(dev, "%s: can't parse \"mboxes\" property\n", __func__);
 		return ERR_PTR(ret);
 	}