dt-bindings: iio: adc: Add ROHM BD79100G

dt-bindings: iio: adc: Add ROHM BD79100G

The ROHM BD79100G is a 12-bit ADC which can be read over SPI. Device has
no MOSI pin. ADC results can be read from MISO by clocking in 16 bits.
The 4 leading bits will be zero, last 12 containig the data.

Device has only VCC supply pin, which acts also as a VFS, determining the
voltage for full 12-bits. Specifying it is mandatory.

This seems identical to the ti,ads7866.

Support ROHM BU79100G using ti,ads7866 as a fallback.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/4907a096eee1f54afae834213cf721b551382d4e.1747203712.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>