ASoC: Add snd_soc_codec_{readable,writable}_register()

Provide the top level ASoC core functions for indicating whether
a given register is readable or writable.

Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/include/sound/soc.h b/include/sound/soc.h
index e208357..2720a9f 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -278,6 +278,10 @@
 void snd_soc_unregister_codec(struct device *dev);
 int snd_soc_codec_volatile_register(struct snd_soc_codec *codec,
 				    unsigned int reg);
+int snd_soc_codec_readable_register(struct snd_soc_codec *codec,
+				    unsigned int reg);
+int snd_soc_codec_writable_register(struct snd_soc_codec *codec,
+				    unsigned int reg);
 int snd_soc_codec_set_cache_io(struct snd_soc_codec *codec,
 			       int addr_bits, int data_bits,
 			       enum snd_soc_control_type control);