linux-wandboard

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: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>