[SCSI] megaraid: remove a spurious IRQ enable

We took this lock with spin_lock() so we should unlock it with
spin_unlock() instead of spin_unlock_irq().  This was introduced in
f2c8dc4 "[SCSI] megaraid_mbox: remove scsi_assign_lock usage".

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Adam Radford <aradford@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/megaraid/megaraid_mbox.c

@@ -2731,7 +2731,7 @@ megaraid_reset_handler(struct scsi_cmnd *scp)
 	}
 
  out:
-	spin_unlock_irq(&adapter->lock);
+	spin_unlock(&adapter->lock);
 	return rval;
 }