ALSA: ASoC: Make OpenFirmware helper include file conditional

The OpenFirmware API headers don't build on all platforms so ensure
that they are not included unless they are being used.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

include/sound/soc-of-simple.h

@@ -7,6 +7,8 @@
 #ifndef _INCLUDE_SOC_OF_H_
 #define _INCLUDE_SOC_OF_H_
 
+#if defined(CONFIG_SND_SOC_OF_SIMPLE) || defined(CONFIG_SND_SOC_OF_SIMPLE_MODULE)
+
 #include <linux/of.h>
 #include <sound/soc.h>
 
@@ -18,4 +20,6 @@ int of_snd_soc_register_platform(struct snd_soc_platform *platform,
 				 struct device_node *node,
 				 struct snd_soc_dai *cpu_dai);
 
+#endif
+
 #endif /* _INCLUDE_SOC_OF_H_ */