fix enter debug mode for locking

fix enter debug mode for locking

added an alternative way to enter debug mode, which does not require restarting the chip.
this will not always work, but in general it will (failure 0.3%), and failure is not a dramatic issue, simply have to use the full sequence.
the user can only access "halt", which uses the full sequence, so the user should not have any problems.
restarting the chip requires reconfiguring the flash module. the doc is very poor, so i'd rather have the two methods, and live with the 0.3%.