dt-bindings: iio: imu: mpu6050: Document invensense,mpu6880

MPU-6880 seems to be very similar to MPU-6500 / MPU-6050 and it works
fine with some minor additions for the mpu6050 driver.
Add a compatible for it to the binding documentation.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Cc: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Link: https://lore.kernel.org/r/20201202104656.5119-1-stephan@gerhold.netSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/imu/invensense,mpu6050.yaml

@@ -25,6 +25,7 @@ properties:
       - invensense,mpu6050
       - invensense,mpu6500
       - invensense,mpu6515
+      - invensense,mpu6880
       - invensense,mpu9150
       - invensense,mpu9250
       - invensense,mpu9255