regmap: return ERR_PTR instead of NULL in regmap_init

The regmap_init documentation states that it will either return a pointer to a
valid regmap structure or a ERR_PTR in case of an error. Currently it returns a
NULL pointer in case no bus or no config was given. Since NULL is not a
ERR_PTR a caller might assume that it is a pointer to a valid regmap structure,
so return a ERR_PTR(-EINVAL) instead.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regmap.c

@@ -139,7 +139,7 @@ struct regmap *regmap_init(struct device *dev,
 	int ret = -EINVAL;
 
 	if (!bus || !config)
-		return NULL;
+		goto err;
 
 	map = kzalloc(sizeof(*map), GFP_KERNEL);
 	if (map == NULL) {