regmap: Add stub for regcache_sync_region()

Added on another branch.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

include/linux/regmap.h

@@ -280,6 +280,13 @@ static inline int regcache_sync(struct regmap *map)
 	return -EINVAL;
 }
 
+static inline int regcache_sync_region(struct regmap *map, unsigned int min,
+				       unsigned int max)
+{
+	WARN_ONCE(1, "regmap API is disabled");
+	return -EINVAL;
+}
+
 static inline void regcache_cache_only(struct regmap *map, bool enable)
 {
 	WARN_ONCE(1, "regmap API is disabled");