video: ARM CLCD: fix return value check in versatile_clcd_init_panel()

In case of error, the function syscon_node_to_regmap() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check should
be replaced with IS_ERR().

Fixes: 25348160 ("video: ARM CLCD: add special panel hook for Versatiles")
Signed-off-by: NWei Yongjun <weiyj.lk@gmail.com>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/fbdev/amba-clcd-versatile.c

@@ -528,9 +528,9 @@ int versatile_clcd_init_panel(struct clcd_fb *fb,
 	versatile_clcd_type = (enum versatile_clcd)clcd_id->data;
 
 	map = syscon_node_to_regmap(np);
-	if (!map) {
+	if (IS_ERR(map)) {
 		dev_err(dev, "no Versatile syscon regmap\n");
-		return -ENODEV;
+		return PTR_ERR(map);
 	}
 
 	switch (versatile_clcd_type) {