dt-bindings: add description for new supported chips

Add missing mpu6000 and new icm20609, icm20689, icm20690, and
iam20680.

Signed-off-by: Jean-Baptiste Maneyrol <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/devicetree/bindings/iio/imu/inv_mpu6050.txt

···
 
 Required properties:
  - compatible : should be one of
+		"invensense,mpu6000"
 		"invensense,mpu6050"
  		"invensense,mpu6500"
 		"invensense,mpu6515"
···
 		"invensense,mpu9250"
 		"invensense,mpu9255"
 		"invensense,icm20608"
+		"invensense,icm20609"
+		"invensense,icm20689"
 		"invensense,icm20602"
+		"invensense,icm20690"
+		"invensense,iam20680"
  - reg : the I2C address of the sensor
  - interrupts: interrupt mapping for IRQ. It should be configured with flags
    IRQ_TYPE_LEVEL_HIGH, IRQ_TYPE_EDGE_RISING, IRQ_TYPE_LEVEL_LOW or