ARM: dts: iwg23s-sbc: Enable watchdog support

This patch enables watchdog support on the iWave iwg23s sbc.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>