clockevents/drivers/cs5535: Migrate to new 'set-state' interface

Migrate cs5535 driver to the new 'set-state' interface provided by
the 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.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Andres Salomon <dilinger@queued.net>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>