davinci: cpuidle - remove useless initialization

The device->state_count is initialized in the cpuidle_register_device
function.

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>