sensor: add driver for AK8975 magnetometer

Add driver for the AK8975 3-axis electonic compass.

Datasheet:
	http://www.akm.com/akm/en/file/datasheet/AK8975.pdf



Change-Id: I427f954396c8991a153e4447d746b855d19cb60d
Origin: Original
Signed-off-by: Bogdan Davidoaia <bogdan.m.davidoaia@intel.com>