ath79: add support for TP-Link TL-WPA8630P (EU) v2.1

ath79: add support for TP-Link TL-WPA8630P (EU) v2.1

This adds support for the TP-Link TL-WPA8630P (EU) in its v2.1
version. The only unique aspect for the firmware compared to v2
layout is the partition layout.

Note that while the EU version has different partitioning for
v2.0 and v2.1, the v2.1 (AU) is supported by the v2-int image.

If you plan to use this device, make sure you have a look at
the Wiki page to check whether the device is supported and
which image needs to be taken.

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

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

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.

Notes
-----

The OEM firmware has 0x620000 to 0x680000 unassigned, so we leave
this empty as well. It is complicated enough already ...

Signed-off-by: Joe Mullally <jwmullally@gmail.com>
[improve partitions, use v2 DTSI, add entry in 02_network, rewrite
and extend commit message]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>