ota_basic example can receive new image via TCP.
However - writing to flash with interrupts disabled causes data loss,
and the TCP flow is very slow to recover. Linux sender quickly ramps up
RTT timer to very long retry intervals, crippling performance &
throughput.
Running the update without the flash writes causes the data to be
received quickly, so this is definitely an issue with the time taken for
the erase cycle.
Progress towards #10
