Document support for the Watchdog Timer (WDT) Controller in the Renesas
R-Car D3 (r8a77995) SoC.

No driver update is needed.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: NSimon Horman <horms+renesas@verge.net.au>
Acked-by: NRob Herring <robh@kernel.org>
Reviewed-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>