watchodg: sama5d4: simplify probe

Because the only way to use the driver is to have a device tree enabling
it, pdev->dev.of_node will never be NULL. Remove the unnecessary check.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>