ASoC: Add a cache_sync bit to the CODEC structure

Add a bit to the CODEC structure indicating if a cache sync is required.
By default this will be set if a cache only write is done to a soc-cache
register cache.  This allows us to avoid syncing the cache back after
using cache only writes if there were no changes.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

include/sound/soc.h

@@ -424,6 +424,7 @@ struct snd_soc_codec {
 
 	unsigned int idle_bias_off:1; /* Use BIAS_OFF instead of STANDBY */
 	unsigned int cache_only:1;  /* Suppress writes to hardware */
+	unsigned int cache_sync:1; /* Cache needs to be synced to hardware */
 
 	/* dapm */
 	u32 pop_time;