Revert "sched: Unify runtime accounting across classes"

This reverts commit 4db5988b which is
commit 5d69eca5 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: Id5db1834e650239105a29f882ee4474968b34ecf
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>