Revert "lib/timerqueue: Rely on rbtree semantics for next timer"

This reverts commit b9a1ac8e which is
commit 511885d7061eda3eb1faf3f57dcc936ff75863f1 upstream.

It breaks the abi and does not resolve an issue that is relevant to
Android devices, so it can be reverted.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I7b35b10c18f91bd132bf33de3572e272591976ae