input: sensors: add power optimization for mpu6050

To save more power, mpu6050 sensor needs vote regulators off after
disable and during suspend. The sensor register context needs to
be restored after it is powered up again.

CRs-fixed: 663426
Change-Id: I06e33c1e2e268c6fa957f0d26bf610ff254b3d22
Signed-off-by: Oliver Wang <mengmeng@codeaurora.org>
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>