regulator: core: Fix format specifier warning

Signed-off-by: Aniroop Mathur <a.mathur@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -3659,7 +3659,7 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	rdev->dev.class = &regulator_class;
 	rdev->dev.parent = dev;
 	dev_set_name(&rdev->dev, "regulator.%lu",
-		     atomic_inc_return(&regulator_no));
+		    (unsigned long) atomic_inc_return(&regulator_no));
 	ret = device_register(&rdev->dev);
 	if (ret != 0) {
 		put_device(&rdev->dev);