Revert "block/mq-deadline: Add cgroup support"

This reverts commit 08a9ad8 ("block/mq-deadline: Add cgroup support")
and a follow-up commit c06bc5a ("block/mq-deadline: Remove a
WARN_ON_ONCE() call"). The added cgroup support has the following issues:

* It breaks cgroup interface file format rule by adding custom elements to a
  nested key-value file.

* It registers mq-deadline as a cgroup-aware policy even though all it's
  doing is collecting per-cgroup stats. Even if we need these stats, this
  isn't the right way to add them.

* It hasn't been reviewed from cgroup side.

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/Kconfig.iosched

@@ -9,12 +9,6 @@ config MQ_IOSCHED_DEADLINE
 	help
 	  MQ version of the deadline IO scheduler.
 
-config MQ_IOSCHED_DEADLINE_CGROUP
-       tristate
-       default y
-       depends on MQ_IOSCHED_DEADLINE
-       depends on BLK_CGROUP
-
 config MQ_IOSCHED_KYBER
 	tristate "Kyber I/O scheduler"
 	default y

block/Makefile

@@ -22,8 +22,6 @@ obj-$(CONFIG_BLK_CGROUP_IOPRIO)	+= blk-ioprio.o
 obj-$(CONFIG_BLK_CGROUP_IOLATENCY)	+= blk-iolatency.o
 obj-$(CONFIG_BLK_CGROUP_IOCOST)	+= blk-iocost.o
 obj-$(CONFIG_MQ_IOSCHED_DEADLINE)	+= mq-deadline.o
-mq-deadline-y += mq-deadline-main.o
-mq-deadline-$(CONFIG_MQ_IOSCHED_DEADLINE_CGROUP)+= mq-deadline-cgroup.o
 obj-$(CONFIG_MQ_IOSCHED_KYBER)	+= kyber-iosched.o
 bfq-y				:= bfq-iosched.o bfq-wf2q.o bfq-cgroup.o
 obj-$(CONFIG_IOSCHED_BFQ)	+= bfq.o