ARM: dts: i.MX51: Add dummy clock to AUDMUX

This patch adds dummy clock for AUDMUX. This change avoids useless
debug message "cannot get clock" during driver initialization.
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx51.dtsi

@@ -455,6 +455,8 @@ ssi1: ssi@83fcc000 {
 			audmux: audmux@83fd0000 {
 				compatible = "fsl,imx51-audmux", "fsl,imx31-audmux";
 				reg = <0x83fd0000 0x4000>;
+				clocks = <&clks 0>;
+				clock-names = "audmux";
 				status = "disabled";
 			};