openocd: Allow using OpenOCD-shipped configs
openocd: Allow using OpenOCD-shipped configs

OpenOCD already ships config files for the EFM32 and EFR32 family, no
need to duplicate them in RIOT; this removes the "file exists" check for
files that are clearly OpenOCD-shipped board configurations, as the
script can't (and shouldn't) know OpenOCD's include paths.

miri64/RIOT,yogo1212/RIOT,authmillenon/RIOT,OlegHahm/RIOT,yogo1212/RIOT,authmillenon/RIOT,basilfx/RIOT,kYc0o/RIOT,kYc0o/RIOT,ant9000/RIOT,kaspar030/RIOT,OlegHahm/RIOT,smlng/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,kaspar030/RIOT,basilfx/RIOT,basilfx/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,basilfx/RIOT,ant9000/RIOT,jasonatran/RIOT,jasonatran/RIOT,miri64/RIOT,smlng/RIOT,jasonatran/RIOT,ant9000/RIOT,kaspar030/RIOT,kaspar030/RIOT,authmillenon/RIOT,OlegHahm/RIOT,yogo1212/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,kaspar030/RIOT,smlng/RIOT,kYc0o/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,miri64/RIOT,smlng/RIOT,ant9000/RIOT,OTAkeys/RIOT,ant9000/RIOT,smlng/RIOT,miri64/RIOT,yogo1212/RIOT,yogo1212/RIOT,authmillenon/RIOT,jasonatran/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,kYc0o/RIOT,OTAkeys/RIOT,miri64/RIOT,authmillenon/RIOT,basilfx/RIOT