docs: block: update and fix tiny error for bfq

The max value of blkio.bfq.weight is 1000, rather than 10000.
And 'weights' have been remove from /sys/block/XXX/queue/iosched.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>