s390/time: Migrate to new 'set-state' interface

Migrate s390 driver to the new 'set-state' interface provided by
clockevents core, the earlier 'set-mode' interface is marked obsolete
now.

This also enables us to implement callbacks for new states of clockevent
devices, for example: ONESHOT_STOPPED.

We weren't doing anything in the ->set_mode() callback. So, this patch
doesn't provide any set-state callbacks.

Cc: Martin Schwidefsky <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Viresh Kumar <[e-mail]>
Signed-off-by: Daniel Lezcano <[e-mail]>

arch/s390/kernel/time.c

···
 	return 0;
 }
 
-static void s390_set_mode(enum clock_event_mode mode,
-			  struct clock_event_device *evt)
-{
-}
-
 /*
  * Set up lowcore and control register of the current cpu to
  * enable TOD clock and clock comparator interrupts.
···
 	cd->rating		= 400;
 	cd->cpumask		= cpumask_of(cpu);
 	cd->set_next_event	= s390_next_event;
-	cd->set_mode		= s390_set_mode;
 
 	clockevents_register_device(cd);