imu: inv_mpu6050: adds device tree bindings

InvenSense MPU-6050 Six-Axis (Gyro + Accelerometer) MEMS MotionTracking Device

http://www.invensense.com/mems/gyro/mpu6050.html

Required properties:

 - compatible : should be "invensense,mpu6050"

 - reg : the I2C address of the sensor

 - interrupt-parent : should be the phandle for the interrupt controller

 - interrupts : interrupt mapping for GPIO IRQ

Example:

	mpu6050@68 {

		compatible = "invensense,mpu6050";

		reg = <0x68>;

		interrupt-parent = <&gpio1>;

		interrupts = <18 1>;

	};