ARM: tegra: asus-tf101: Enable S/PDIF and HDMI audio

Enable S/PDIF controller to enable HDMI audio support on ASUS TF101.
Use nvidia,fixed-parent-rate property that prevents audio rate conflict
between S/PDIF and I2S.
Tested-by: NRobert Eckelmann <longnoserob@gmail.com>
Signed-off-by: NDmitry Osipenko <digetx@gmail.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra20-asus-tf101.dts

@@ -436,8 +436,16 @@
 		};
 	};
 
+	spdif@70002400 {
+		status = "okay";
+
+		nvidia,fixed-parent-rate;
+	};
+
 	i2s@70002800 {
 		status = "okay";
+
+		nvidia,fixed-parent-rate;
 	};
 
 	serial@70006040 {