Working IN SYNC swo output from a freshly powered on stlinkv2

Critical missing piece was calling writemem32 with a length in words,
when it needed a length in bytes.  So most of my commands weren't
actually working :)

Usage:

python hack.py
connect
swo_start
swo_read
swo_read
swo_read
.... until you're bored.

This is just PoC code at this point