ASoC: nau8822: add support for supply regulators

ASoC: nau8822: add support for supply regulators

Alexey Charkov <alchark@flipper.net> says:

The Nuvoton NAU8822 codec has four power supply pins: VDDA, VDDB, VDDC
and VDDSPK, which must be online and stable before the device can be
accessed over I2C. On boards where these rails are software-controlled,
probing the codec before the regulators are up results in -ENXIO errors
during register access.

This short series adds optional regulator support to both the device
tree binding and the driver, so platforms that need explicit power
sequencing can describe and enforce it:

Link: https://patch.msgid.link/20260525-nau8822-reg-v2-0-7d37ae393e46@flipper.net