* Invensense MPU6xxx Gyro + Accelerometer
* Invensense MPU9xxx Gyro + Accelerometer + Compass

Required properties:
- compatible: The driver is compatible with
  "invensense,itg3500"
  "invensense,mpu3050"
  "invensense,mpu6050"
  "invensense,mpu9150"
  "invensense,mpu6500"
  "invensense,mpu9250"
  "invensense,mpu6xxx"
- reg: the I2C address
- interrupt-parent: the interrupt controller that it is attached to.
- interrupts: The intterrupt property of device node.
- invensense,int_config: Bits [7:3] of the int config register.
- invensense,level_shifter: 0: VLogic, 1: VDD
- invensense,orientation: the orientation matricies are 3x3 rotation matricies
  that are applied to the data to rotate from the mounting orientation to the
  platform orientation. The values must be one of 0, 1, or -1(0xff in byte
  array) and each row and column should have exactly 1 non-zero value.
- invensense,sec_slave_type: secondary slave device type
  0: SECONDARY_SLAVE_TYPE_NONE
  1: SECONDARY_SLAVE_TYPE_ACCEL
  2: SECONDARY_SLAVE_TYPE_COMPASS
  3: SECONDARY_SLAVE_TYPE_PRESSURE
- invensense,key: key for MPL library.

Example:

mpu9250@69 {
	compatible = "invensense,mpu9250";
	reg = <0x69>;
	interrupt-parent = <&gpio>;
	interrupts = <144 0x01>;
	invensense,int_config = <0x10>;
	invensense,level_shifter = <0>;
	invensense,orientation = [01 00 00 00 01 00 00 00 01];
	invensense,sec_slave_type = <0>;
	invensense,key = [4e cc 7e eb f6 1e 35 22 00 34 0d 65 32 e9 94 89];
};

