board/msba2: Added stdio_init()
board/msba2: Added stdio_init()

The MSB-A2 uses a custom boot up sequence and does not have a cpu_init(). This
adds the missing call to stdio_init() to that custom boot up sequence.

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