cpu/cortexm_common: introduce cpu_jump_to_image()
cpu/cortexm_common: introduce cpu_jump_to_image()

This new function allows to jump to another execution
environment (VTOR) located at a certain (aligned) address.
It's used to boot firmwares at another location than
`CPU_FLASH_BASE`.

The user needs to ensure that the CPU using this feature
is able to be initialised at least twice while jumping
to the RIOT `reset_handler_default` function, since it
initialises the CPU again (calls cpu_init()).

Co-authored-by: Kaspar Schleiser <3da571cc5fc4657e2d4751aae14f3a8f7e01ed00@schleiser.de>

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