tests/mtd_flashpage: adapt test for msp430
tests/mtd_flashpage: adapt test for msp430

- msp430 holds the ISR vector in the last page, avoid
  erasing that page during test.

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