ARM: dts: imx6ul-isiot: Pass the required '#sound-dai-cells'

DTC now warns about missing #sound-dai-cells:

/sound/simple-audio-card,codec: Missing property '#sound-dai-cells' in
node /soc/aips-bus@2100000/i2c@21a0000/codec@a or bad phandle
(referred from sound-dai[0])

Pass the required '#sound-dai-cells' property to fix it.
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6ul-isiot.dtsi

@@ -142,6 +142,7 @@ &i2c1 {
 	sgtl5000: codec@a {
 		compatible = "fsl,sgtl5000";
 		reg = <0x0a>;
+		#sound-dai-cells = <0>;
 		clocks = <&clks IMX6UL_CLK_OSC>;
 		clock-names = "mclk";
 		VDDA-supply = <&reg_3p3v>;