blk-mq: set default timeout as 30 seconds

blk-mq: set default timeout as 30 seconds

commit e56f698bd0720e17f10f39e8b0b5b446ad0ab22c upstream.

It is reasonable to set default timeout of request as 30 seconds instead of
30000 ticks, which may be 300 seconds if HZ is 100, for example, some arm64
based systems may choose 100 HZ.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Fixes: c76cbbcf4044 ("blk-mq: put blk_queue_rq_timeout together in blk_mq_init_queue()"
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>