PCI hotplug: fix lock imbalance in pciehp

set_lock_status omits mutex_unlock in fail path. Add the omitted
unlock.

As a result a lockup caused by this can be triggered from userspace
by writing 1 to /sys/bus/pci/slots/.../lock often enough.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Reviewed-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/hotplug/pciehp_core.c

@@ -126,8 +126,10 @@ static int set_lock_status(struct hotplug_slot *hotplug_slot, u8 status)
 	mutex_lock(&slot->ctrl->crit_sect);
 
 	/* has it been >1 sec since our last toggle? */
-	if ((get_seconds() - slot->last_emi_toggle) < 1)
+	if ((get_seconds() - slot->last_emi_toggle) < 1) {
+		mutex_unlock(&slot->ctrl->crit_sect);
 		return -EINVAL;
+	}
 
 	/* see what our current state is */
 	retval = get_lock_status(hotplug_slot, &value);