ASoC: mediatek: remove "simple-mfd" in the example

Remove compatible string "simple-mfd" in the example as we have
already added devm_of_platform_populate() in the parent driver.
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/mt2701-afe-pcm.txt

@@ -53,7 +53,7 @@ See ../arm/mediatek/mediatek,audsys.txt for details about the parent node.
 Example:
 
 	audsys: audio-subsystem@11220000 {
-		compatible = "mediatek,mt2701-audsys", "syscon", "simple-mfd";
+		compatible = "mediatek,mt2701-audsys", "syscon";
 		...
 
 		afe: audio-controller {