Revert "block: introduce the BFQ-v6r2 I/O sched for 3.4"

This reverts commit 61abf795ea4aa9e6c417f86f660df621dcc8eb4b.
Revert "BFQ/ZEN/VR/SIO/FIOPS  IO/Schedulers"

This reverts commit cc225fa964f56e1a7f4da9391766fccbd9f7c8e9.