v2: Rename vdd to vddio and reword

Some LEDs controllers are used with external pull-up for the interrupt
line and the I2C lines, so we might need to enable a regulator to bring
the lines into usable state. Otherwise, this might cause spurious
interrupts and reading from I2C will fail.

Implement support for "vddio-supply" that is enabled by the aw2013 driver
so that the regulator gets enabled when needed.