ipq40xx: add support for GL.iNet GL-B2200

ipq40xx: add support for GL.iNet GL-B2200

This patch adds supports for the GL-B2200 router.

Specifications:
  - SOC: Qualcomm IPQ4019 ARM Quad-Core
  - RAM: 512 MiB
  - Flash: 16 MiB NOR - SPI0
  - EMMC: 8GB EMMC
  - ETH: Qualcomm QCA8075
  - WLAN1: Qualcomm Atheros QCA4019 2.4GHz 802.11b/g/n 2x2
  - WLAN2: Qualcomm Atheros QCA4019 5GHz 802.11n/ac W2 2x2
  - WLAN3: Qualcomm Atheros QCA9886 5GHz 802.11n/ac W2 2x2
  - INPUT: Reset, WPS
  - LED: Power, Internet
  - UART1: On board pin header near to LED (3.3V, TX, RX, GND), 3.3V without pin - 115200 8N1
  - UART2: On board with BLE module
  - SPI1: On board socket for Zigbee module

Update firmware instructions:
Please update the firmware via U-Boot web UI (by default at 192.168.1.1, following instructions found at
https://docs.gl-inet.com/en/3/troubleshooting/debrick/).
Normal sysupgrade, either via CLI or LuCI, is not possible from stock firmware.
Please do use the *gl-b2200-squashfs-emmc.img file, gunzipping the produced *gl-b2200-squashfs-emmc.img.gz one first.

What's working:
- WiFi 2G, 5G
- WPA2/WPA3

Not tested:
- Bluetooth LE/Zigbee

Credits goes to the original authors of this patch.

V1->V2:
- updates *arm-boot-add-dts-files.patch correctly (sorry, my mistake)
- add uboot-envtools support
V2->V3:
- Li Zhang updated official patch to fix wrong MAC address on wlan0 (PCI) interface
V3->V4:
- wire up sysupgrade

Signed-off-by: Li Zhang <li.zhang@gl-inet.com>
[fix tab and trailing space, document what's working and what's not]
Signed-off-by: TruongSinh Tran-Nguyen <i@truongsinh.pro>
[rebase on top of master, address remaining comments]
Signed-off-by: Enrico Mioso <mrkiko.rs@gmail.com>
[remove redundant check in platform.sh]
Signed-off-by: Daniel Golle <daniel@makrotopia.org>