The Samsung SoC watchdog driver always required providing a clock
(either through platform data or from DT).  However when bindings were
added in commit 9487a9cc ("watchdog: s3c2410: Add support for device
tree based probe"), they missed the requirement of clock.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>