ARM: dts: imx6qdl-tx6: remove undocumented karo,imx6qdl-tx6-sgtl5000 and keep only simple-audio-card

Remove the undocumented and unused compatible karo,imx6qdl-tx6-sgtl5000 and
retain only the generic simple-audio-card sound configuration.

The karo,imx6qdl-tx6-sgtl5000 compatible is not documented and is not
referenced by any in-kernel driver. The audio setup is already fully
described using simple-audio-card, which is the standard and supported
binding for this hardware configuration.

No known users (such as uboot) rely on karo,imx6qdl-tx6-sgtl5000.

Fix below CHECK_DTBS warnings:
arch/arm/boot/dts/nxp/imx/imx6dl-tx6dl-comtft.dtb: /sound: failed to match any schema with compatible: ['karo,imx6qdl-tx6-sgtl5000', 'simple-audio-card']

Signed-off-by: Frank Li <Frank.Li@nxp.com>

Author: nxpfrankli

arch/arm/boot/dts/nxp/imx/imx6qdl-tx6.dtsi

@@ -148,8 +148,7 @@
 	};
 
 	sound {
-		compatible = "karo,imx6qdl-tx6-sgtl5000",
-			     "simple-audio-card";
+		compatible = "simple-audio-card";
 		simple-audio-card,name = "imx6qdl-tx6-sgtl5000-audio";
 		pinctrl-names = "default";
 		pinctrl-0 = <&pinctrl_audmux>;