watchdog: Orion: Fix possible null-deference in orion_wdt_probe

If the DT does not include a regs parameter then the null res
would be dereferenced.

Signed-off-by: Jason Gunthorpe <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/orion_wdt.c

···
 	wdt_tclk = clk_get_rate(clk);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
 	wdt_reg = devm_ioremap(&pdev->dev, res->start, resource_size(res));
 	if (!wdt_reg)
 		return -ENOMEM;