regmap: Allow regmap_update_bits() users to detect changes

Some users of regmap_update_bits() would like to be able to tell their
users if they actually did an update so provide a variant which also
returns a flag indicating if an update took place. We could return a
tristate in the return value of regmap_update_bits() but this makes the
API more cumbersome to use and doesn't fit with the general zero for
success idiom we have.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 81dfe0a..a83e4a0 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -138,6 +138,9 @@
 		     size_t val_count);
 int regmap_update_bits(struct regmap *map, unsigned int reg,
 		       unsigned int mask, unsigned int val);
+int regmap_update_bits_check(struct regmap *map, unsigned int reg,
+			     unsigned int mask, unsigned int val,
+			     bool *change);
 
 int regcache_sync(struct regmap *map);
 void regcache_cache_only(struct regmap *map, bool enable);