ARM: tegra: acer-a500: Enable S/PDIF and HDMI audio

Enable S/PDIF controller to enable HDMI audio support on Acer A500.
Use nvidia,fixed-parent-rate property that prevents audio rate conflict
between S/PDIF and I2S.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra20-acer-a500-picasso.dts

@@ -376,8 +376,16 @@ pta {
 		};
 	};
 
+	tegra_spdif: spdif@70002400 {
+		status = "okay";
+
+		nvidia,fixed-parent-rate;
+	};
+
 	tegra_i2s1: i2s@70002800 {
 		status = "okay";
+
+		nvidia,fixed-parent-rate;
 	};
 
 	uartb: serial@70006040 {