This change fixes the case where CHDR_W < ITEM_W*NIPC.
It also adds a state machine to stall the input to the pyld_fifo to
ensure that the pkt_info_fifo will not overflow. Previously in some
cases it allowed the same word to be inserted into the pyld_fifo
multiple times.
Original-commit: b862eda69cf41c7044a1805324f2fcfef5b0ba3d