An unofficial but likely effective method is to setup a serial connection, wired Ethernet, and serve the correct firmware via TFTP.
See Gateway not connecting to WLAN/LAN after firmware update for a situation with the similar platform of the 7258
An unofficial but likely effective method is to setup a serial connection, wired Ethernet, and serve the correct firmware via TFTP.
See Gateway not connecting to WLAN/LAN after firmware update for a situation with the similar platform of the 7258