By now neither wsn-v1_4 nor telosb driver implementation handles RXFIFO correctly. When FIFOP fires, the RXFIFO should be always read, because at least one packet was received. If FIFO goes down, the driver should check if FIFOP is high and call SFLUSHRX if true (otherwise do nothing).

(migrated from https://github.com/RIOT-OS/boards/issues/27)