Add support for: AD4111, AD4112, AD4114, AD4115, AD4116.

AD411x family ADCs support a VCOM pin. The purpose of this pin is to
offer a dedicated common-mode voltage input for single-ended channels.
This pin is specified as supporting a differential channel with VIN10 on
model AD4116.

AD4111/AD4112 support current channels. Support is implemented using
single-channel and "adi,current-channel".
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Dumitru Ceclan <dumitru.ceclan@analog.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240607-ad4111-v7-2-97e3855900a0@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>