bsg: fix the deadlock on discarding done commands

The previous commit introduced a deadlock in discarding commands,
because we forget to unlock the bd spinlock.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

block/bsg.c

@@ -471,6 +471,7 @@ static int bsg_complete_all_commands(struct bsg_device *bd)
 			spin_unlock_irq(&bd->lock);
 			break;
 		}
+		spin_unlock_irq(&bd->lock);
 
 		bc = bsg_get_done_cmd(bd);
 		if (IS_ERR(bc))