We add the required and optional properties for evb board.
See the [0] to get the detail information.

[0]:
Documentation/devicetree/bindings/net/rockchip-dwmac.txt
Signed-off-by: NRoger Chen <roger.chen@rock-chips.com>
Signed-off-by: NCaesar Wang <wxt@rock-chips.com>
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>