Revert "block: introduce the BFQ-v4 I/O sched for 3.1"

This reverts commit 1fa991bfab03b435bb2194da50f2ab449c83f58b.
Revert "block: cgroups, kconfig, build bits for BFQ-v4-3.1"

This reverts commit b6e36b8b7160737e4e214a269dabade5280c12cc.

Conflicts:
	block/Makefile
Revert "block: prepare I/O context code for BFQ-v4 for 3.1"

This reverts commit d44add735c6d60051d0c1abf017199231fa59c47.

Conflicts:
	block/Kconfig.iosched
[PATCH 1/4] block: prepare I/O context code for BFQ-v6r2 for 3.1

Conflicts:
	block/Kconfig.iosched
[PATCH 2/4] block: cgroups, kconfig, build bits for BFQ-v6r2-3.1

Conflicts:
	include/linux/cgroup_subsys.h
[PATCH 2/4] block: cgroups, kconfig, build bits for BFQ-v6r2-3.1

Conflicts:
	block/Makefile
[PATCH 3/4] block: introduce the BFQ-v6r2 I/O sched for 3.1
[PATCH 4/4] block, bfq: add Early Queue Merge (EQM) to BFQ-v6r2 for 3.1.0
block: bfq-iosched.c: tweak default values