input: sensor: enable MPU6050 motion detection

When MPU6050 is run in interrupt mode, its build in accelerometer will
stay powered on and the device is woken up when significant motion is
detected. This is part of sensor low power implementation.

Change-Id: I979d586413fd364d5fc787888fbd2369dcab83c9
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>