sensor: ak8975: add support for MPU9150

The AK8975 chip can be packaged together with a MPU6050 chip, resulting
in a MPU9150 chip. In this format, the MPU6050 part of the MPU9150 chip
needs to be turned on and pass-through mode enable in order to communicate
with the AK8975 chip.

Datasheet:
	http://43zrtwysvxb2gf29r5o0athu.wpengine.netdna-cdn.com/wp-content/uploads/2015/02/MPU-9150-Datasheet.pdf

Register Map:
	http://43zrtwysvxb2gf29r5o0athu.wpengine.netdna-cdn.com/wp-content/uploads/2015/02/MPU-9150-Register-Map.pdf



Change-Id: I120dff11c187689e2e6968c812aae2e3e3578bc6
Signed-off-by: Bogdan Davidoaia <bogdan.m.davidoaia@intel.com>