dt-bindings: iio: proximity: Add RF Digital RFD77402 ToF sensor

dt-bindings: iio: proximity: Add RF Digital RFD77402 ToF sensor

The RF Digital RFD77402 is a Time-of-Flight (ToF) proximity and distance
sensor that provides absolute and highly accurate distance measurements
from 100 mm up to 2000 mm over an I2C interface. It includes an optional
interrupt pin that signals when new measurement data is ready.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Shrikant Raskar <raskar.shree97@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>