tftp: code diet, and I think retransmits were broken.

function                                             old     new   delta
static.errcode_str                                     -      32     +32
tftp_main                                            359     345     -14
tftp_bb_error_msg                                     32       -     -32
.rodata                                           130931  130899     -32
tftp                                                1720    1558    -162
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 0/3 up/down: 32/-240)          Total: -208 bytes

1 file changed