Revert "oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup"

This reverts commit ed5d4efb which is
commit e4a38402 upstream.

It breaks the kernel ABI and should not be an issue for Android at this
point in time.  If it is, it can come back in a different, abi-stable
form.

Bug: 161946584
Fixes: ed5d4efb ("oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup")
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I729614c373a7b28546376913e719bbaf6dd306a9