regmap: async: Add missing return

Let's only write once...

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 3d23675..dd82acf 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1036,6 +1036,8 @@
 			kfree(async->work_buf);
 			kfree(async);
 		}
+
+		return ret;
 	}
 
 	trace_regmap_hw_write_start(map->dev, reg,