ath79: add support for TP-Link TL-WPA8630P v2

ath79: add support for TP-Link TL-WPA8630P v2

The TL-WPA8630P v2 is a HomePlug AV2 compatible device with a QCA9563 SoC
and 2.4GHz and 5GHz WiFi modules.

Specifications
--------------

  - QCA9563 750MHz, 2.4GHz WiFi
  - QCA9888 5GHz WiFi
  - 8MiB SPI Flash
  - 128MiB RAM
  - 3 GBit Ports (QCA8337)
  - PLC (QCA7550)

MAC address assignment
----------------------

WiFi 2.4GHz and LAN share the same MAC address as printed on the label.
5GHz WiFi uses LAN-1, based on assumptions from similar devices.

LAN Port assignment
-------------------

While there are 3 physical LAN ports on the device, there will be 4
visible ports in OpenWrt. The fourth port (internal port 5) is used
by the PowerLine Communication SoC and thus treated like a regular
LAN port.

Versions
--------

Note that both TL-WPA8630 and TL-WPA8630P, as well as the different
country-versions, differ in partitioning, and therefore shouldn't be
cross-flashed.

This adds support for the two known partitioning variants of the
TL-WPA8630P, where the variants can be safely distinguished via the
tplink-safeloader SupportList. For the non-P variants (TL-WPA8630),
at least two additional partitioning schemes exist, and the same
SupportList entry can have different partitioning.
Thus, we don't support those officially (yet).

Also note that the P version for Germany (DE) requires the international
image version, but is properly protected by SupportList.

In any case, please check the OpenWrt Wiki pages for the device
before flashing anything!

Installation
------------

Installation is possible from the OEM web interface. Make sure to
install the latest OEM firmware first, so that the PLC firmware is
at the latest version. However, please also check the Wiki page
for hints according to altered partitioning between OEM firmware
revisions.

Additional thanks to Jon Davies and Joe Mullally for bringing
order into the partitioning mess.

Signed-off-by: Andreas Böhler <dev@aboehler.at>
[minor DTS adjustments, add label-mac-device, drop chosen, move
common partitions to DTSI, rename de to int, add AU support strings,
adjust TPLINK_BOARD_ID, create common node in generic-tp-link.mk,
adjust commit message]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>