ar40xx_switch: add initial switch for the IPQ4018/IPQ4019.

[adrian]

Summary

This switch is based off of the AR8327/AR8337 external switch/PHY.
However unlike the AR8327/AR8337 it itself doesn't have any PHYs;
instead an external PHY connects to it using the PSGMII port.

This code is inspired by the ar40xx code in openwrt, which itself
is based on the Qualcomm QCA-SSDK. Both of these sources are, amusingly,
BSD licenced - and thus I have included some of the comments in the
hardware workaround paths to document some of the magic numbers.

[manu]

sys/dev/etherswitch/ar40xx/ar40xx_hw.h

5

I guess that your copyrights should be 2021-2022

28

Not needed for new file since git doesn't expend this.

33

We usually don't put extern

sys/dev/etherswitch/ar40xx/ar40xx_main.c

303

Why not directly OF_finddevice("/soc/mdio") ?

sys/dev/etherswitch/ar40xx/ar40xx_var.h

86

That doesn't seems to be needed except in the attach function.

[adrian]

update dates

[adrian]

sys/dev/etherswitch/ar40xx/ar40xx_var.h

86

It's going to in some later commits, where I need to go reach into the mdio device tree entries to pull out the /phy/ config parameters. Yeah. Ugh.

[adrian]

sys/dev/etherswitch/ar40xx/ar40xx_hw.h

28

Ugh I'm going to have to go find all of these and delete them aren't i

[adrian]

n/a

[adrian]

address more things

[adrian]

update ids