boards/mcb2388: update SPI configuration
boards/mcb2388: update SPI configuration

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