ath79: add support for TP-LINK Archer C7 v4

TP-Link Archer C7 v4 is a dual-band AC1750 router, based on the
Qualcomm/Atheros QCA9561 SoC + QCA9880.

Specification:

- 775/650/258 MHz (CPU/DDR/AHB)
- 128 MB of RAM (DDR2)
- 16 MB of FLASH (SPI NOR)
- 3T3R 2.4 GHz
- 3T3R 5 GHz
- 5x 10/100/1000 Mbps Ethernet
- 7x LED, 2x button
- UART header on PCB

Flash instruction:
1. Upload openwrt-ath79-generic-tplink_archer-c7-v4-squashfs-factory.bin
   via Web interface

Flash instruction using TFTP recovery:
1. Set PC to fixed ip address 192.168.0.66
2. Download openwrt-ath79-generic-tplink_archer-c7-v4-squashfs-factory.bin
   and rename it to ArcherC7v4_tp_recovery.bin
3. Start a tftp server with the file tp_recovery.bin in its root directory
4. Turn off the router
5. Press and hold Reset button
6. Turn on router with the reset button pressed and wait ~15 seconds
7. Release the reset button and after a short time
   the firmware should be transferred from the tftp server
8. Wait ~30 second to complete recovery.

Signed-off-by: Oldřich Jedlička <oldium.pro@gmail.com>

target/linux/ath79/image/generic-tp-link.mk

@@ -75,6 +75,18 @@ define Device/tplink_archer-c7-v2
 endef
 TARGET_DEVICES += tplink_archer-c7-v2
 
+define Device/tplink_archer-c7-v4
+  $(Device/tplink-safeloader-uimage)
+  ATH_SOC := qca9563
+  IMAGE_SIZE := 15104k
+  DEVICE_TITLE := TP-LINK Archer C7 v4
+  DEVICE_PACKAGES := kmod-usb-core kmod-usb2 kmod-usb-ledtrig-usbport kmod-ath10k-ct ath10k-firmware-qca988x-ct
+  TPLINK_BOARD_ID := ARCHER-C7-V4
+  BOARDNAME := ARCHER-C7-V4
+  SUPPORTED_DEVICES += archer-c7-v4
+endef
+TARGET_DEVICES += tplink_archer-c7-v4
+
 define Device/tplink_archer-c7-v5
   $(Device/tplink-safeloader-uimage)
   ATH_SOC := qca9563