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

Migrate qcom 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.

Periodic mode isn't supported by the driver and so the callback isn't
provided anymore.

Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Andy Gross <agross@codeaurora.org>
Cc: David Brown <davidb@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>