ARM: kirkwood: Add RSTOUT 'reg' entry to devicetree

In order to support multiplatform builds the watchdog devicetree binding
was modified and now the 'reg' property is specified to need two
entries. This commit adds the second entry as-per the new specification.

Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>