Revert "blk-cgroup: support to track if policy is online"

This reverts commit 5d5ea4f9 which is
commit dfd6200a upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Ibd89626cc871d0f045806ebbcad500ee6fa1dfbd
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>