edbg.inc.mk: allow flashing with an offset in rom
edbg.inc.mk: allow flashing with an offset in rom

Allow flashing with an offset in ROM from the rom base address.
It reuses `IMAGE_OFFSET` configuration variable name from `openocd.sh`.

This will allow flashing multiple images with different flash operations.

RIOT-OS/RIOT,toonst/RIOT,basilfx/RIOT,authmillenon/RIOT,jasonatran/RIOT,cladmi/RIOT,lazytech-org/RIOT,yogo1212/RIOT,toonst/RIOT,kaspar030/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,BytesGalore/RIOT,kbumsik/RIOT,smlng/RIOT,lazytech-org/RIOT,kbumsik/RIOT,x3ro/RIOT,kYc0o/RIOT,gebart/RIOT,lazytech-org/RIOT,mfrey/RIOT,jasonatran/RIOT,A-Paul/RIOT,mfrey/RIOT,kbumsik/RIOT,biboc/RIOT,miri64/RIOT,cladmi/RIOT,toonst/RIOT,gebart/RIOT,jasonatran/RIOT,gebart/RIOT,OTAkeys/RIOT,yogo1212/RIOT,kaspar030/RIOT,aeneby/RIOT,toonst/RIOT,aeneby/RIOT,gebart/RIOT,mtausig/RIOT,basilfx/RIOT,x3ro/RIOT,yogo1212/RIOT,josephnoir/RIOT,mtausig/RIOT,miri64/RIOT,rfuentess/RIOT,A-Paul/RIOT,ant9000/RIOT,kaspar030/RIOT,miri64/RIOT,rfuentess/RIOT,lazytech-org/RIOT,biboc/RIOT,rfuentess/RIOT,mfrey/RIOT,lazytech-org/RIOT,OTAkeys/RIOT,avmelnikoff/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,OTAkeys/RIOT,josephnoir/RIOT,smlng/RIOT,x3ro/RIOT,yogo1212/RIOT,biboc/RIOT,OlegHahm/RIOT,smlng/RIOT,cladmi/RIOT,authmillenon/RIOT,aeneby/RIOT,x3ro/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,aeneby/RIOT,mtausig/RIOT,yogo1212/RIOT,BytesGalore/RIOT,mfrey/RIOT,kbumsik/RIOT,avmelnikoff/RIOT,authmillenon/RIOT,OlegHahm/RIOT,A-Paul/RIOT,jasonatran/RIOT,kaspar030/RIOT,BytesGalore/RIOT,mfrey/RIOT,josephnoir/RIOT,miri64/RIOT,authmillenon/RIOT,ant9000/RIOT,smlng/RIOT,OlegHahm/RIOT,basilfx/RIOT,mtausig/RIOT,ant9000/RIOT,ant9000/RIOT,josephnoir/RIOT,kYc0o/RIOT,toonst/RIOT,smlng/RIOT,aeneby/RIOT,kYc0o/RIOT,mtausig/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,ant9000/RIOT,gebart/RIOT,BytesGalore/RIOT,basilfx/RIOT,cladmi/RIOT,x3ro/RIOT,cladmi/RIOT,OlegHahm/RIOT,kbumsik/RIOT,josephnoir/RIOT,A-Paul/RIOT,avmelnikoff/RIOT,biboc/RIOT,miri64/RIOT,authmillenon/RIOT,kaspar030/RIOT,rfuentess/RIOT,rfuentess/RIOT,A-Paul/RIOT,BytesGalore/RIOT,basilfx/RIOT,authmillenon/RIOT,avmelnikoff/RIOT,OTAkeys/RIOT,biboc/RIOT,avmelnikoff/RIOT,jasonatran/RIOT