This argument was not being considered since blk-mq was set by default,
so removed this documentation to avoid confusion.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMarcos Paulo de Souza <marcos.souza.org@gmail.com>

.txt file is now .rst
Signed-off-by: NJens Axboe <axboe@kernel.dk>