CH422G I/O expander

A driver for the CH422G I2C-bus I/O expander by WCH, commonly used on Waveshare ESP32 display boards to drive display/touch reset and enable lines.

Exposes EXIO0-7 as a GPIO_CONTROLLER_TYPE device. The chip has no register to configure per-pin direction and no readback for its output register, so only output pins are supported and the driver keeps a local shadow of the last written value.