interface/ftdi/xds100v2.cfg: default to reset state and ask user to release it later

interface/ftdi/xds100v2.cfg: default to reset state and ask user to release it later

This adapter is special and needs a reset sequence to be performed
before operation. Since there're no suitable hooks to do that, we have
no choice but to ask the user to manually add the necessary commands
to his or her config file.

Change-Id: I48fb4276e77529768266840221b68c3ae26801e1
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/1884
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>