davinci: cpuidle - remove the ops

With one function handling the idle state and a single variable,
the usage of the davinci_ops is overkill.

This patch removes these ops and simplify the code.

Furthermore, the 'driver_data' field is no longer used, we have
1 of the 3 remaining user of this field removed.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Len Brown <len.brown@intel.com>