ipmi/powernv: Fix minor locking bug

commit ad1ed2a9 upstream.

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>
Cc: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.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;
 	}