The 'def' local variable became unused after commit f382fb0b ("block: remove
legacy IO schedulers"), let's remove it.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NHisao Tanabe <xtanabe@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>