Program serial FLASH chips using an FTDIx232H based debug probe.
You have just upgraded the bootloader on your board to enable that one missing feature that you needed. Great. But you messed up the build and now your board is a brick. Not as great.
Fortunately, you have a Bus Blaster v4 from Dangerous Prototypes that you can use with dangerspi to reprogram the board with a working version. Typically you would do something like this:
$ ./dangerspi.py erase 0 0x100000
$ ./dangerspi.py write 0 0x100000 </path/to/shiny/loader.bin