rvrt bfq

Revert "block: cgroups, kconfig, build bits for BFQ-v6-3.4"

This reverts commit d029a6e57e3cfa3bfc7ec6f107d78d67065098ce.
Revert "block: introduce the BFQ-v6 I/O sched for 3.4"

This reverts commit fd1de8fae5c422b8845f8b6c7d0a3a0670a7234f.
Apply BFQ 3.4.0-v6r2:

http://algo.ing.unimo.it/people/paolo/disk_sched/sources.php

Signed-off-by: Paul Beeler <sparksco@gmail.com>