kernel: rtl8367b: add configuration for extif2

kernel: rtl8367b: add configuration for extif2

Both rtl8367b and rtl8367s have two extended interface
rtl8367rb: 5 port + 2*RGMII/MII
rtl8367s:  5 port + SGMII/HSGMI + RGMII/MII
(?)rtl8367sb:  5 port + 2*RGMII/MII
These interfaces correspond to EXT1 and EXT2 (ports 6 and 7 respectivly).

This patch allow to configure EXT2 in dts-file:

	rtl8367rb {
		compatible = "realtek,rtl8367b";
		cpu_port = <7>;
		realtek,extif2 = <1 0 1 1 1 1 1 1 2>;
		mii-bus = <&mdio0>;
		phy_id = <29>;
	};

Signed-off-by: Serge Vasilugin <vasilugin@yandex.ru>
[fix indent, replace magic value, alter commit message]
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>