mailbox: pcc: Avoid using the uninitialized variable 'dev'

Smatch static checker warns:

  |  drivers/mailbox/pcc.c:292 pcc_mbox_request_channel()
  |  error: uninitialized symbol 'dev'.

Fix the same by using pr_err instead of dev_err as the variable 'dev'
is uninitialized at that stage.

Fixes: ce028702 ("mailbox: pcc: Move bulk of PCCT parsing into pcc_mbox_probe")
Cc: Jassi Brar <jassisinghbrar@gmail.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/pcc.c

@@ -289,7 +289,7 @@ pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
 	pchan = chan_info + subspace_id;
 	chan = pchan->chan.mchan;
 	if (IS_ERR(chan) || chan->cl) {
-		dev_err(dev, "Channel not found for idx: %d\n", subspace_id);
+		pr_err("Channel not found for idx: %d\n", subspace_id);
 		return ERR_PTR(-EBUSY);
 	}
 	dev = chan->mbox->dev;