[media] exynos4-is: Fix potential null pointer dereference in mipi-csis.c

When 'node' is NULL, the print statement tries to dereference it.
Hence replace the variable with the one that is accessible.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/exynos4-is/mipi-csis.c

@@ -746,7 +746,7 @@ static int s5pcsis_parse_dt(struct platform_device *pdev,
 	node = v4l2_of_get_next_endpoint(node, NULL);
 	if (!node) {
 		dev_err(&pdev->dev, "No port node at %s\n",
-					node->full_name);
+				pdev->dev.of_node->full_name);
 		return -EINVAL;
 	}
 	/* Get port node and validate MIPI-CSI channel id. */