Revert "cgroup/rstat: Fix forceidle time in cpu.stat"

This reverts commit 35016776 which is
commit c4af66a9 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: If49f05db1ffaee1ce0c8750cfa0439e353498c91
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>