BFQ hierarchical scheduling support

configname: CONFIG_BFQ_GROUP_IOSCHED

Linux Kernel Configuration
└─>Enable the block layer
└─>IO Schedulers
└─>BFQ hierarchical scheduling support
In linux kernel since version 4.2 (release Date: 2015-08-30)  
Enable hierarchical scheduling in BFQ, using the blkio
(cgroups-v1) or io (cgroups-v2) controller.

depends
CONFIG_BLK_CGROUP
CONFIG_BLOCK
CONFIG_IOSCHED_BFQ