kernel: rtl8366_smi: explicitly set phy addr for switch

kernel: rtl8366_smi: explicitly set phy addr for switch

By default rtl8366_smi use phy addr 0 at mii-bus to access switch registers.
This patch allow to set it explicitly in dts-file:

	rtl8367 {
		compatible = "realtek,rtl8367b";
		phy-id = <29>; /* switch address at mii-bus */
		realtek,extif2 = <1 0 1 1 1 1 1 1 2>;
		mii-bus = <&mdio>;
		cpu-port = <7>;
	}

Use default 0 address if not set.
Backward compatibility tested on tplink archer c2 v1 (rtl8367rb switch)

Signed-off-by: Serge Vasilugin <vasilugin@yandex.ru>
[code style fixes, add explicit phy_id assignment in probe_plat, use
phy-id instead of phy_id for of property name]
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
[rebase]
Signed-off-by: Gaspare Bruno <gaspare@anlix.io>
[added phy_id to struct rtl8366_smi]
Signed-off-by: Mieczyslaw Nalewaj <namiltd@yahoo.com>