ARM: dts: mmp3: add Dell Wyse 3020 machine

ARM: dts: mmp3: add Dell Wyse 3020 machine

This is a Dell Wyse thin client, variously referred to as "Ariel",
"3020" or "Tx0D" where "x" stands for the software it was shipped with.
I somewhat arbitrarily chose "ariel".

There are bits missing, because the drivers are not in and bindings are not
settled yet:

* Things missing from mmp3.dtsi:
  HSIC controller and its PHY (only the internal Ethernet is connected
  here, the hub with external USB2 ports is connected to the U2O controller
  that works well), Vivante GC2000 GPU

* &twsi1/regulator@19
  Marvell 88pm867 power regulator

* &twsi3/vga-dvi-encoder@76
  Chrontel CH7033B-BF VGA & DVI encoder

* &twsi3/sound-codec@30
  Sound chip, probably a Marvell 88ce156

* &twsi4/embedded-controller@58
  ENE KB3930QF Embedded Controller, also seems to be connected to &ssp4.
  Might not need a driver -- about the only useful thing it can do is to
  reboot the machine when tickled via some GPIO lines.

Also there seems to be something at &twsi1 address 0x50.

Link: https://lore.kernel.org/r/20191022152837.3553524-1-lkundrak@v3.sk
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Olof Johansson <olof@lixom.net>