[media] exynos-gsc: avoid build warning without CONFIG_OF

When building the exynos-gsc driver with CONFIG_OF disabled, we get
a warning about an out-of-bounds access:

drivers/media/platform/exynos-gsc/gsc-core.c: In function 'gsc_probe':
drivers/media/platform/exynos-gsc/gsc-core.c:1078:34: error: array subscript is above array bounds [-Werror=array-bounds]

This is harmless because the driver will never be used without CONFIG_OF,
but it's better to avoid the warning anyway. Checking the return value
of of_alias_get_id() for an error condition is probably a good idea
anyway, and it makes sure the compiler can verify that we don't get
into that situation.

Fixes: 26a7ed9c1819 ("[media] exynos-gsc: remove an always false condition")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/exynos-gsc/gsc-core.c

@@ -1063,13 +1063,17 @@ static int gsc_probe(struct platform_device *pdev)
 	struct resource *res;
 	struct gsc_driverdata *drv_data = gsc_get_drv_data(pdev);
 	struct device *dev = &pdev->dev;
-	int ret = 0;
+	int ret;
 
 	gsc = devm_kzalloc(dev, sizeof(struct gsc_dev), GFP_KERNEL);
 	if (!gsc)
 		return -ENOMEM;
 
-	gsc->id = of_alias_get_id(pdev->dev.of_node, "gsc");
+	ret = of_alias_get_id(pdev->dev.of_node, "gsc");
+	if (ret < 0)
+		return ret;
+
+	gsc->id = ret;
 	if (gsc->id >= drv_data->num_entities) {
 		dev_err(dev, "Invalid platform device id: %d\n", gsc->id);
 		return -EINVAL;