x86/xen/time: Migrate to new set-state interface

Migrate xen 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.

Callbacks aren't implemented for modes where we weren't doing anything.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: xen-devel@lists.xenproject.org (moderated list:XEN HYPERVISOR INTERFACE)
Link: http://lkml.kernel.org/r/881eea6e1a3d483cd33e044cd34827cce26a57fd.1437042675.git.viresh.kumar@linaro.org


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