Nuvoton NAU88L21 audio codec

This device supports I2C only.

Required properties:
  - compatible : Must be "nuvoton,nau8821"

  - reg : the I2C address of the device. This is either 0x1B (CSB=0) or 0x54 (CSB=1).

Optional properties:
  - nuvoton,jkdet-enable: Enable jack detection via JKDET pin.
  - nuvoton,jkdet-pull-enable: Enable JKDET pin pull. If set - pin pull enabled,
      otherwise pin in high impedance state.
  - nuvoton,jkdet-pull-up: Pull-up JKDET pin. If set then JKDET pin is pull up, otherwise pull down.
  - nuvoton,jkdet-polarity: JKDET pin polarity. 0 - active high, 1 - active low.

  - nuvoton,vref-impedance: VREF Impedance selection
      0 - Open
      1 - 25 kOhm
      2 - 125 kOhm
      3 - 2.5 kOhm

  - nuvoton,micbias-voltage: Micbias voltage level.
      0 - VDDA
      1 - VDDA
      2 - VDDA * 1.1
      3 - VDDA * 1.2
      4 - VDDA * 1.3
      5 - VDDA * 1.4
      6 - VDDA * 1.53
      7 - VDDA * 1.53

  - nuvoton,jack-insert-debounce: number from 0 to 7 that sets debounce time to 2^(n+2) ms
  - nuvoton,jack-eject-debounce: number from 0 to 7 that sets debounce time to 2^(n+2) ms

  - nuvoton,dmic-clk-threshold: the ADC threshold of DMIC clock.
  - nuvoton,key_enable: Headset button detection switch.

Example:

  headset: nau8821@1b {
      compatible = "nuvoton,nau8821";
      reg = <0x1b>;
      interrupt-parent = <&gpio>;
      interrupts = <23 IRQ_TYPE_LEVEL_LOW>;
      nuvoton,jkdet-enable;
      nuvoton,jkdet-pull-enable;
      nuvoton,jkdet-pull-up;
      nuvoton,jkdet-polarity = <GPIO_ACTIVE_LOW>;
      nuvoton,vref-impedance = <2>;
      nuvoton,micbias-voltage = <6>;
      nuvoton,jack-insert-debounce = <7>;
      nuvoton,jack-eject-debounce = <7>;
      nuvoton,dmic-clk-threshold = 3072000;
  };
