Revert "sched/fair: Add new cfs_rq.h_nr_runnable"

This reverts commit 3edcabcf which is
commit c2a295bf 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: I4766fa12fb97adfee94fa31a9130bfa6dadf0080
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>