ARM: dts: imx6ul-geam: Remove invalid sgtl5000 property

As per sgtl5000.yaml, 'clock-names' is not a valid property.

Remove it to fix the following schema warning:

imx6ul-isiot-nand.dtb: codec@a: Unevaluated properties are not allowed ('clock-names' was unexpected)
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/nxp/imx/imx6ul-geam.dts

@@ -148,7 +148,6 @@ sgtl5000: codec@a {
 		reg = <0x0a>;
 		#sound-dai-cells = <0>;
 		clocks = <&clks IMX6UL_CLK_OSC>;
-		clock-names = "mclk";
 		VDDA-supply = <&reg_3p3v>;
 		VDDIO-supply = <&reg_3p3v>;
 		VDDD-supply = <&reg_1p8v>;