ASoC: tegra: tegra210_admaif: Fix compile warning with CONFIG_PM=n

Fix trivial compile warnings wrt unused functions by adding
__maybe_unused prefix:
  sound/soc/tegra/tegra210_admaif.c:232:12: warning: 'tegra_admaif_runtime_resume' defined but not used [-Wunused-function]
  sound/soc/tegra/tegra210_ahub.c:567:12: warning: 'tegra_ahub_runtime_suspend' defined but not used [-Wunused-function]

Fixes: f74028e1 ("ASoC: tegra: Add Tegra210 based ADMAIF driver")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20200803141850.23713-3-tiwai@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/tegra/tegra210_admaif.c

@@ -219,7 +219,7 @@ static const struct regmap_config tegra186_admaif_regmap_config = {
 	.cache_type		= REGCACHE_FLAT,
 };
 
-static int tegra_admaif_runtime_suspend(struct device *dev)
+static int __maybe_unused tegra_admaif_runtime_suspend(struct device *dev)
 {
 	struct tegra_admaif *admaif = dev_get_drvdata(dev);
 
@@ -229,7 +229,7 @@ static int tegra_admaif_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int tegra_admaif_runtime_resume(struct device *dev)
+static int __maybe_unused tegra_admaif_runtime_resume(struct device *dev)
 {
 	struct tegra_admaif *admaif = dev_get_drvdata(dev);