ARM: tegra_defconfig: Enable S/PDIF driver

Enable Tegra20 S/PDIF driver. It's a part of HDMI audio subsystem on
Tegra.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/configs/tegra_defconfig

@@ -231,6 +231,7 @@ CONFIG_SND_HDA_CODEC_HDMI=y
 CONFIG_SND_SOC=y
 CONFIG_SND_SOC_TEGRA=y
 CONFIG_SND_SOC_TEGRA20_I2S=y
+CONFIG_SND_SOC_TEGRA20_SPDIF=y
 CONFIG_SND_SOC_TEGRA30_I2S=y
 CONFIG_SND_SOC_TEGRA_RT5640=y
 CONFIG_SND_SOC_TEGRA_WM8753=y