Initialize a LFSR register object
lfsr = lfsr_init(deg)
LFSR polynomial degree (from 0 to 15)
Resulting LFSR object (can be used with the function lfsr_process)
The LFSR register size will be 1 + degree, and the polynomial choosen so as to have the longest minimal sequence.
Xilinx xapp-052.pdf (July 7, 1996), page 5