NBD doesn't care about limiting the segment size, let the user push the
largest bio's they want.  This allows us to control the request size
solely through max_sectors_kb.
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>