Same as TP-Link TL-XDR608x, this router comes with locked vendor
loader. Add U-Boot build for replacement loader for this device.
Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Link: https://github.com/openwrt/openwrt/pull/15930
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
