arm64: dts: renesas: r8a774c0-cat874: Add RWDT support

Enable RWDT and use 60 seconds as default timeout.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Chris Paterson <chris.paterson2@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>