mediatek: filogic: kn-1812: add interrupt support for phy

mediatek: filogic: kn-1812: add interrupt support for phy

In the latest vendor firmware, changes have been identified in the DTS.
Support for interrupts for the Realtek RTL8261BE has been added.

Decompiled DTS fragment:

phy-gmac3 {
        compatible = "ethernet-phy-ieee802.3-c45";
        interrupt-parent = <0x1a>;
        interrupts = <0x02 0x08>;
        #address-cells = <0x01>;
        #size-cells = <0x00>;
        reg = <0x1b>;
        phy-mode = "usxgmii";
        linux,phandle = <0x30>;
        phandle = <0x30>;
};

Signed-off-by: Maxim Anisimov <maxim.anisimov.ua@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/22575
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>