This is useful debugging information that will be used in the blk-mq
debugfs directory.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NOmar Sandoval <osandov@fb.com>

Changed 'weight' to 'busy'.
Signed-off-by: NJens Axboe <axboe@fb.com>