update 8169:
- setting the station address doesn't appear to be allowed.  avoid
doing it.  the linux driver doesn't set it either.
- check for a supported mac directly in the pnp function to avoid
surprises later.
- since we can't easily disallow receiving packets larger than our
buffers (some chips behave very badly), just discard fragmented packets.
- add a few new mac types.  the mac numbers are in line with
the linux driver.  there appears to be some disagreement about
what the mac numbers are.  all the new macs have been tested,
though it's tempting to add all known macs.

cavet: there may be a mtu setting that may not exist in
the standard kernel, due to the fact i added jumbo support
for aoe:
/n/sources/plan9//sys/src/9/pc/ether8169.c:1174,1179 - ether8169.c:1206,1212
  	edev->irq = ctlr->pcidev->intl;
  	edev->tbdf = ctlr->pcidev->tbdf;
  	edev->mbps = 100;
+ 	edev->maxmtu = Mtu;