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

This reverts commit d20f28f0 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: I6a6d4e3d775d02a5d20be35c1175e3a3cbcd33a0
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>