input: sensors: add mpu6050 accel sensor calibration

Add mpu6050 accelerometer calibrate feature to calibrate
sensor raw data and it just for factory calibration now.
It provides static bias to compensate raw data more normally.

Change-Id: Ibd316bb1e14d4c6784f1b168e16f537270626cf6
Signed-off-by: Daqing Chen <chendaqing@codeaurora.org>