PM / devfreq: imx-bus: use NULL to pass a null pointer rather than zero

The 3rd argument to the function of_get_property is a pointer and it is
being passed using 0. Use NULL instead.

Cleans up sparse warning:
warning: Using plain integer as NULL pointer
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/devfreq/imx-bus.c

@@ -59,7 +59,7 @@ static int imx_bus_init_icc(struct device *dev)
 	struct imx_bus *priv = dev_get_drvdata(dev);
 	const char *icc_driver_name;
 
-	if (!of_get_property(dev->of_node, "#interconnect-cells", 0))
+	if (!of_get_property(dev->of_node, "#interconnect-cells", NULL))
 		return 0;
 	if (!IS_ENABLED(CONFIG_INTERCONNECT_IMX)) {
 		dev_warn(dev, "imx interconnect drivers disabled\n");