dt-bindings: iio: adc: adding support for PAC193X

This is the device tree schema for iio driver for
Microchip PAC193X series of Power Monitors with Accumulator.

Signed-off-by: Marius Cristea <marius.cristea@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240222164206.65700-2-marius.cristea@microchip.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>