regmap: Devices using format_write don't support bulk operations

Set the use_single_rw flag for devices that use format_write() since
format_write() doesn't support any form of block operation.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 0a05a70..fcd69ff 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -341,6 +341,9 @@
 		break;
 	}
 
+	if (map->format.format_write)
+		map->use_single_rw = true;
+
 	if (!map->format.format_write &&
 	    !(map->format.format_reg && map->format.format_val))
 		goto err_map;