Stock firmware has a vendor-defined tail at the end of uImage for image
validation. This patch enables OpenWrt installation from stock firmware
without having to access the UART console.
Installation via web interface:
1. Flash **initramfs** image through the stock web interface.
2. Boot into OpenWrt and perform sysupgrade with sysupgrade image.
Signed-off-by: Sungbo Eo <mans0n@gorani.run>
(cherry picked from commit be3e98ce26)
2d3a93335a