boards/frdm: fix flashing from invalid state
boards/frdm: fix flashing from invalid state

When flashing some applications the flasher sometimes gets stuck which
prevents flashing after.
It may be from a specific firmware or operation but do not have one yet.
Connect with reset asserted fix flashing from this state.

miri64/RIOT,kYc0o/RIOT,OTAkeys/RIOT,mtausig/RIOT,OlegHahm/RIOT,x3ro/RIOT,yogo1212/RIOT,mtausig/RIOT,josephnoir/RIOT,kaspar030/RIOT,miri64/RIOT,mtausig/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,jasonatran/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,yogo1212/RIOT,mtausig/RIOT,aeneby/RIOT,jasonatran/RIOT,authmillenon/RIOT,authmillenon/RIOT,josephnoir/RIOT,OTAkeys/RIOT,kaspar030/RIOT,x3ro/RIOT,RIOT-OS/RIOT,josephnoir/RIOT,authmillenon/RIOT,toonst/RIOT,miri64/RIOT,RIOT-OS/RIOT,basilfx/RIOT,yogo1212/RIOT,yogo1212/RIOT,toonst/RIOT,kYc0o/RIOT,miri64/RIOT,ant9000/RIOT,x3ro/RIOT,rfuentess/RIOT,rfuentess/RIOT,smlng/RIOT,kaspar030/RIOT,aeneby/RIOT,x3ro/RIOT,kYc0o/RIOT,ant9000/RIOT,miri64/RIOT,aeneby/RIOT,basilfx/RIOT,authmillenon/RIOT,toonst/RIOT,yogo1212/RIOT,rfuentess/RIOT,smlng/RIOT,josephnoir/RIOT,OlegHahm/RIOT,ant9000/RIOT,mtausig/RIOT,authmillenon/RIOT,kaspar030/RIOT,jasonatran/RIOT,OTAkeys/RIOT,basilfx/RIOT,kaspar030/RIOT,basilfx/RIOT,smlng/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,toonst/RIOT,rfuentess/RIOT,ant9000/RIOT,rfuentess/RIOT,josephnoir/RIOT,x3ro/RIOT,smlng/RIOT,yogo1212/RIOT,aeneby/RIOT,basilfx/RIOT,smlng/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,kYc0o/RIOT,aeneby/RIOT,toonst/RIOT,authmillenon/RIOT,kYc0o/RIOT,jasonatran/RIOT,ant9000/RIOT