ipmi/powernv: Fix minor locking bug

If ipmi_powernv_recv(...) is called without a current message it
prints a warning and returns. However it fails to release the message
lock causing the system to dead lock during any subsequent IPMI
operations.

This error path should never normally be taken unless there are bugs
elsewhere in the system.

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/ipmi_powernv.c

@@ -125,6 +125,7 @@ static int ipmi_powernv_recv(struct ipmi_smi_powernv *smi)
 	spin_lock_irqsave(&smi->msg_lock, flags);
 
 	if (!smi->cur_msg) {
+		spin_unlock_irqrestore(&smi->msg_lock, flags);
 		pr_warn("no current message?\n");
 		return 0;
 	}