zero: power: make sure DT2W exists before announcing support
zero: power: make sure DT2W exists before announcing support

Change-Id: Idebc44a32f84160f23514f711b4ddaf9c8fe8627

TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common