dt-bindings: iio: dac: adding support for Microchip MCP47FEB02

dt-bindings: iio: dac: adding support for Microchip MCP47FEB02

This is the device tree schema for iio driver for Microchip
MCP47F(E/V)B(0/1/2)1, MCP47F(E/V)B(0/1/2)2, MCP47F(E/V)B(0/1/2)4 and
MCP47F(E/V)B(0/1/2)8 series of buffered voltage output Digital-to-Analog
Converters with nonvolatile or volatile memory and an I2C Interface.

The families support up to 8 output channels.

The devices can be 8-bit, 10-bit and 12-bit.

Signed-off-by: Ariana Lazar <ariana.lazar@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>