ASoC: davinci-pcm: Add empty functions for !CONFIG_SND_DAVINCI_SOC builds

To save drivers using davinci-pcm and edma-pcm the need to fiddle with
!CONFIG_SND_DAVINCI_SOC in their code.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/davinci/davinci-pcm.h

@@ -29,7 +29,17 @@ struct davinci_pcm_dma_params {
 	unsigned int fifo_level;
 };
 
+#if IS_ENABLED(CONFIG_SND_DAVINCI_SOC)
 int davinci_soc_platform_register(struct device *dev);
 void davinci_soc_platform_unregister(struct device *dev);
+#else
+static inline int davinci_soc_platform_register(struct device *dev)
+{
+	return 0;
+}
+static inline void davinci_soc_platform_unregister(struct device *dev)
+{
+}
+#endif /* CONFIG_SND_DAVINCI_SOC */
 
 #endif