notes: in the flasher source, it's designed for more than one
   interface, and use of the lpc chip is guarded by this:
   uint8_t lpc_test(void) {
           nibble_hw_init();
           lpc_init();
           if (lpc_read_address(0xFFFFFFFF)==-1) return 0;
           return 1;
   }
   flashrom itself doesn't seem to care about that check (although I
   haven't looked in the source): it just probes for a bunch of chips
   anyway.
   so I guess the thing to do would be to look for the first lines that
   are engaged, and see where failure starts.