block: sunvdc: don't run hw queue synchronously from irq context

vdc_blk_queue_start() may be called from irq context, so we can't run
queue via blk_mq_start_hw_queues() since we never allow to run queue
from irq context. Use blk_mq_start_stopped_hw_queues(q, true) to fix
this issue.

Fixes: fa182a1f

 ("sunvdc: convert to blk-mq")
Reported-by: Anatoly Pugachev <matorola@gmail.com>
Tested-by: Anatoly Pugachev <matorola@gmail.com>
Cc: Anatoly Pugachev <matorola@gmail.com>
Cc: sparclinux@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>