boards/native: fix default value of PORT
boards/native: fix default value of PORT

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