ASoC: rt5663: rename rt5668 as rt5663 v2

The "rt5668" codec supported in this driver is actually a revision
of "rt5663". So the patch is renamed to "rt5663 v2"
Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/rt5663.txt

-RT5663/RT5668 audio CODEC
+RT5663 audio CODEC
 
 This device supports I2C only.
 
 Required properties:
 
-- compatible : One of "realtek,rt5663" or "realtek,rt5668".
+- compatible : "realtek,rt5663".
 
 - reg : The I2C address of the device.
 
@@ -12,7 +12,7 @@ Required properties:
 
 Optional properties:
 
-Pins on the device (for linking into audio routes) for RT5663/RT5668:
+Pins on the device (for linking into audio routes) for RT5663:
 
   * IN1P
   * IN1N