ASoC: add rt5663 codec driver

This is the initial codec driver for both rt5663 rt5668 codec.

Signed-off-by: John Lin <john.lin@realtek.com>
Signed-off-by: Jack Yu <jack.yu@realtek.com>
Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/rt5663.txt

@@ -0,0 +1,30 @@
+RT5663/RT5668 audio CODEC
+
+This device supports I2C only.
+
+Required properties:
+
+- compatible : One of "realtek,rt5663" or "realtek,rt5668".
+
+- reg : The I2C address of the device.
+
+- interrupts : The CODEC's interrupt output.
+
+Optional properties:
+
+Pins on the device (for linking into audio routes) for RT5663/RT5668:
+
+  * IN1P
+  * IN1N
+  * IN2P
+  * IN2N
+  * HPOL
+  * HPOR
+
+Example:
+
+codec: rt5663@12 {
+	compatible = "realtek,rt5663";
+	reg = <0x12>;
+	interrupts = <7 IRQ_TYPE_EDGE_FALLING>;
+};