regulator: ad5398: Constify regulator_desc

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/regulator/ad5398.c b/drivers/regulator/ad5398.c
index 26d23ad..1bd3e72 100644
--- a/drivers/regulator/ad5398.c
+++ b/drivers/regulator/ad5398.c
@@ -184,7 +184,7 @@
 	.is_enabled = ad5398_is_enabled,
 };
 
-static struct regulator_desc ad5398_reg = {
+static const struct regulator_desc ad5398_reg = {
 	.name = "isink",
 	.id = 0,
 	.ops = &ad5398_ops,