- Correct the maxsize parameter when creating the mbufs busdma tag to
reflect the actual requirement of dc(4).
- Move the KASSERT in dc_newbuf() to the right spot.
- Also convert the TX side to take advantage of bus_dmamap_load_mbuf_sg(9).
- Move the comment regarding dc_start_locked() to the right spot.
MFC after: 2 weeks