sched_tick_suspend() and sched_tick_resume() only call rcu related
functions, so eliminate them and do the rcu_idle_timer*() calling in
rcu_idle_[enter|exit]().
Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Dario Faggioli <dfaggioli@suse.com> Acked-by: Julien Grall <julien@xen.org> Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>