- In bce_rx_intr(), use BUS_DMASYNC_POSTREAD instead of
BUS_DMASYNC_POSTWRITE, as we want to "read" from the
rx page chain pages.
- Document why we need to do PREWRITE after we have updated
the rx page chain pages.
- In bce_intr(), use BUS_DMASYNC_POSTREAD and
BUS_DMASYNC_PREREAD when before and after CPU "reading"
the status block.
- Adjust some nearby style mismatches/etc.
Pointed out by: yongari
Approved by: davidch (no objection) but bugs are mine :)