ROCKCHIP multi dais driver

Required properties:
- compatible: "rockchip,multi-dais"
  - "rockchip,rk3308-multi-dais"
- dais: The phandle of sub dais, such i2s, pdm etc.
- capture,channel-mapping: map channels, one for each in dais,
  capture,channel-mapping = <2 6> means:
  i2s 2ch + pdm 6ch --> total 8ch capture.
- playback,channel-mapping: map channels, one for each in dais.
  playback,channel-mapping = <4 4> means:
  i2s 4ch + pdm 4ch --> total 8ch playback.

Required properties for i2s 16ch:
- rockchip,grf: the phandle of the syscon node for GRF register.

Optional properties:
- frame-master: bool properties, frame master, one for each in dais.
- bitclock-master: bool properties, bit clock master, one for each in dais.
- bitclock-inversion: bool properties, bit clock inversion, one for each in dais.
- frame-inversion: bool properties, frame clock inversion, one for each in dais.

Example:

multi_dais: multi-dais {
	status = "okay";
	compatible = "rockchip,multi-dais";
	dais = <&i2s_8ch_2>, <&pdm_8ch>;
	capture,channel-mapping = <2 6>;
	playback,channel-mapping = <4 4>;
	bitclock-master = <1 0>;
	frame-master = <1 0>;
	bitclock-inversion = <0 0>;
	frame-inversion = <0 0>;
	rockchip,grf = <&grf>;
};

&i2s_8ch_2 {
	status = "okay";
	rockchip,no-dmaengine;
};

&pdm_8ch {
	status = "okay";
	rockchip,no-dmaengine;
};

vad-sound {
	status = "okay";
	compatible = "rockchip,multicodecs-card";
	rockchip,card-name = "rockchip,rk3308-vad";
	rockchip,cpu = <&multi_dais>;
	rockchip,codec = <&acodec>, <&vad>;
};