Support carrier locked modems (access /readonly/fsg/* files) #25
Description
Currently tqftpserv only accepts /readonly/ paths that start with /readonly/firmware/image/.
Carrier modems need access to the fsg partition:
[TQFTP] RRQ: /readonly/fsg/nora/latam/customer/personal_arg.mbn (mode=octet rsize=0 seek=0)
invalid path /readonly/fsg/nora/latam/customer/personal_arg.mbn, rejecting
[TQFTP] unable to open /readonly/fsg/nora/latam/customer/personal_arg.mbn (2), reject