drm: rcar-du: Fix the return check of of_parse_phandle and of_find_device_by_node

of_parse_phandle and of_find_device_by_node may return NULL
which cannot be checked by IS_ERR.

Fixes: 8de707ae ("drm: rcar-du: kms: Initialize CMM instances")
Signed-off-by: Wang Xiaojun <wangxiaojun11@huawei.com>
Reported-by: Hulk Robot <hulkci@huawei.com>
Acked-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

[Replace -ENODEV with -EINVAL]
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_kms.c

@@ -700,10 +700,10 @@ static int rcar_du_cmm_init(struct rcar_du_device *rcdu)
 		int ret;
 
 		cmm = of_parse_phandle(np, "renesas,cmms", i);
-		if (IS_ERR(cmm)) {
+		if (!cmm) {
 			dev_err(rcdu->dev,
 				"Failed to parse 'renesas,cmms' property\n");
-			return PTR_ERR(cmm);
+			return -EINVAL;
 		}
 
 		if (!of_device_is_available(cmm)) {
@@ -713,10 +713,10 @@ static int rcar_du_cmm_init(struct rcar_du_device *rcdu)
 		}
 
 		pdev = of_find_device_by_node(cmm);
-		if (IS_ERR(pdev)) {
+		if (!pdev) {
 			dev_err(rcdu->dev, "No device found for CMM%u\n", i);
 			of_node_put(cmm);
-			return PTR_ERR(pdev);
+			return -EINVAL;
 		}
 
 		of_node_put(cmm);