libanyio: factor out ethernet and serial transport level details from lbp16

you must use lbp16_init with proper board type to setup SEND and RECV function pointers in lbp16.c
then you must call lbp16_send_packet and lbp16_recv_packet which will point to current transport layer functions

Signed-off-by: Michael Geszkiewicz <micges@wp.pl>