ASoC: tegra: Staticize some functions in tegra30_i2s.c

'tegra30_i2s_startup' and 'tegra30_i2s_shutdown' are used only in this file and
hence made static. Fixes the following sparse warnings:
sound/soc/tegra/tegra30_i2s.c:74:5: warning:
symbol 'tegra30_i2s_startup' was not declared. Should it be static?
sound/soc/tegra/tegra30_i2s.c:101:6: warning:
symbol 'tegra30_i2s_shutdown' was not declared. Should it be static?

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/tegra/tegra30_i2s.c

@@ -71,7 +71,7 @@ static int tegra30_i2s_runtime_resume(struct device *dev)
 	return 0;
 }
 
-int tegra30_i2s_startup(struct snd_pcm_substream *substream,
+static int tegra30_i2s_startup(struct snd_pcm_substream *substream,
 			struct snd_soc_dai *dai)
 {
 	struct tegra30_i2s *i2s = snd_soc_dai_get_drvdata(dai);
@@ -98,7 +98,7 @@ int tegra30_i2s_startup(struct snd_pcm_substream *substream,
 	return ret;
 }
 
-void tegra30_i2s_shutdown(struct snd_pcm_substream *substream,
+static void tegra30_i2s_shutdown(struct snd_pcm_substream *substream,
 			struct snd_soc_dai *dai)
 {
 	struct tegra30_i2s *i2s = snd_soc_dai_get_drvdata(dai);