iio: adc: ad7606: enable Vdrive power supply

Enable Vdrive power supply. The "vdrive-supply" property is mandatory,
already declared in fdt dt_schema.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Link: https://patch.msgid.link/20250530-wip-bl-ad7606-reference-voltages-v2-1-d5e1ad7e6f14@baylibre.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>