ath79: add support for TP-Link Archer A7

ath79: add support for TP-Link Archer A7

This patch adds support for TP-Link Archer A7

Specification:
- SOC: QCA9563
- Flash: 16 MiB (SPI)
- RAM: 128 MiB (DDR2)
- Ethernet: 4x 1Gbps LAN + 1x 1Gbps WAN
- Wireless:
  - 2.4GHz (bgn) SoC internal
  - 5GHz (ac) QCA988x
- USB: 1x USB 2.0 port
- Button: 1x power, 1x reset, 1x wps
- LED: 10x LEDs
- UART: holes in PCB
  - Vcc, GND, RX, TX from ethernet port side
  - 115200n8

Flash instructions:

Upload openwrt-ath79-generic-tplink_archer-a7-v5-squashfs-factory.bin
via the Webinterface.

Flash instruction using tftp recovery:

1. Connect the computer to one of the LAN ports of the Archer A7
2. Set the computer IP to 192.168.0.66
3. Start a tftp server with the OpenWrt factory image in the tftp
   root directory renamed to ArcherC7v5_tp_recovery.bin
2. Connect power cable to Archer A7, press and hold the reset button
   and turn the router on
3. Keep the reset button pressed for ~5 seconds
4. Wait ~150 seconds to complete flashing

Changes since first revision:

  - Flash instructions using stock image webinterface
  - Changed "Version 5" in model string to "v5"
  - Split DTS file in qca9563_tplink_archer-x7-v5.dtsi
    and qca9563_tplink_archer-a7-v5.dts
  - Firmware image is now build with dynamic partitioning
  - Default to ath10k-ct

Changes since second revision:
  - Changed uboot@0 to uboot@20000 in DTS file
  - Fixed ordering issue in board led script
  - Specify firmware partition format in DTS file
  - Rebased Makefile device definition on common
    Device/tplink-safeloader-uimage definition
  - Merged switch section in network script
    (same configuration as tplink,tl-wdr3600
    and tplink,tl-wdr4300)

Signed-off-by: Karl-Felix Glatzer <karl.glatzer@gmx.de>