dt-bindings: iio: adc: Add BD7910[0,1,2,3]

dt-bindings: iio: adc: Add BD7910[0,1,2,3]

The ROHM BD79100, BD79101, BD79102, BD79103 are very similar ADCs as the
ROHM BD79104. The BD79100 has only 1 channel. BD79101 has 2 channels and
the BD79102 has 4 channels. Both BD79103 and BD79104 have 4 channels,
and, based on the data sheets, they seem identical from the software
point-of-view.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/0874c5933cf56430b9440d19ff46f746e4897952.1755504346.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>