cpu/cc2538: Flush the RX FIFO (if overflowed) after a receive
cpu/cc2538: Flush the RX FIFO (if overflowed) after a receive

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