regulator: Mark supply_name const and duplicate it as such

The supply_name member of struct regulator can be const as we
don't change it in the regulator core. Furthermore, when we copy
the supply name we can use kstrdup_const() here to avoid a copy
if the name is in the ro data section.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -1343,7 +1343,7 @@ static struct regulator *create_regulator(struct regulator_dev *rdev,
 			/* non-fatal */
 		}
 	} else {
-		regulator->supply_name = kstrdup(supply_name, GFP_KERNEL);
+		regulator->supply_name = kstrdup_const(supply_name, GFP_KERNEL);
 		if (regulator->supply_name == NULL)
 			goto overflow_err;
 	}
@@ -1799,7 +1799,7 @@ static void _regulator_put(struct regulator *regulator)
 	put_device(&rdev->dev);
 	mutex_unlock(&rdev->mutex);
 
-	kfree(regulator->supply_name);
+	kfree_const(regulator->supply_name);
 	kfree(regulator);
 
 	module_put(rdev->owner);

drivers/regulator/internal.h

@@ -29,7 +29,7 @@ struct regulator {
 	int uA_load;
 	int min_uV;
 	int max_uV;
-	char *supply_name;
+	const char *supply_name;
 	struct device_attribute dev_attr;
 	struct regulator_dev *rdev;
 	struct dentry *debugfs;