x86/lguest/timer: Migrate to new set-state interface

Migrate lguest 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 while switching modes other than in shutdown
mode and so those are not implemented.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-and-tested-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: linaro-kernel@lists.linaro.org
Cc: Alexander Kuleshov <kuleshovmail@gmail.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: lguest@lists.ozlabs.org (open list:LGUEST)
Link: http://lkml.kernel.org/r/b96f1c308f4523255c5394a4e6e13f2b67685402.1437042675.git.viresh.kumar@linaro.org


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>