realtek: add support for RTL8218E

realtek: add support for RTL8218E

ZyXEL XGS1250-12 Rev.B1 has RTL8218E compared to RTL8218D in Rev.A1
but both of them seem very similar and pin compatible. Therefore
they can share the same phy_driver callbacks.

PHY identifier is set based on the datasheet from
  https://github.com/plappermaul/realtek-doc/blob/main/RTL8218E-CG_Datasheet.pdf

Before:

[    2.120161] rtl83xx-switch switch@1b000000 lan1 (uninitialized): PHY [mdio-bus:00] driver [Generic PHY] (irq=POLL)
[    2.134581] rtl83xx-switch switch@1b000000 lan2 (uninitialized): PHY [mdio-bus:01] driver [Generic PHY] (irq=POLL)
[    2.149043] rtl83xx-switch switch@1b000000 lan3 (uninitialized): PHY [mdio-bus:02] driver [Generic PHY] (irq=POLL)
[    2.163498] rtl83xx-switch switch@1b000000 lan4 (uninitialized): PHY [mdio-bus:03] driver [Generic PHY] (irq=POLL)
[    2.177963] rtl83xx-switch switch@1b000000 lan5 (uninitialized): PHY [mdio-bus:04] driver [Generic PHY] (irq=POLL)
[    2.192435] rtl83xx-switch switch@1b000000 lan6 (uninitialized): PHY [mdio-bus:05] driver [Generic PHY] (irq=POLL)
[    2.207009] rtl83xx-switch switch@1b000000 lan7 (uninitialized): PHY [mdio-bus:06] driver [Generic PHY] (irq=POLL)
[    2.221474] rtl83xx-switch switch@1b000000 lan8 (uninitialized): PHY [mdio-bus:07] driver [Generic PHY] (irq=POLL)

After:

[    2.119165] rtl83xx-switch switch@1b000000 lan1 (uninitialized): PHY [mdio-bus:00] driver [REALTEK RTL8218E] (irq=POLL)
[    2.132880] rtl83xx-switch switch@1b000000 lan2 (uninitialized): PHY [mdio-bus:01] driver [REALTEK RTL8218E] (irq=POLL)
[    2.146727] rtl83xx-switch switch@1b000000 lan3 (uninitialized): PHY [mdio-bus:02] driver [REALTEK RTL8218E] (irq=POLL)
[    2.160580] rtl83xx-switch switch@1b000000 lan4 (uninitialized): PHY [mdio-bus:03] driver [REALTEK RTL8218E] (irq=POLL)
[    2.174367] rtl83xx-switch switch@1b000000 lan5 (uninitialized): PHY [mdio-bus:04] driver [REALTEK RTL8218E] (irq=POLL)
[    2.188270] rtl83xx-switch switch@1b000000 lan6 (uninitialized): PHY [mdio-bus:05] driver [REALTEK RTL8218E] (irq=POLL)
[    2.202140] rtl83xx-switch switch@1b000000 lan7 (uninitialized): PHY [mdio-bus:06] driver [REALTEK RTL8218E] (irq=POLL)
[    2.216047] rtl83xx-switch switch@1b000000 lan8 (uninitialized): PHY [mdio-bus:07] driver [REALTEK RTL8218E] (irq=POLL)

Based-on-patch-by: Antanas Bruzas <[email protected]>
Signed-off-by: Thomas Martitz <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20068
Signed-off-by: Hauke Mehrtens <[email protected]>