driver's probe() routine fills in in nic->irqno.  This is so that
non-interrupt-capable legacy drivers which set nic->irqno=0 will end
up reporting IRQ#0 via PXENV_UNDI_GET_INFORMATION; this in turn means
that the calling PXE NBP will (should) hook the timer interrupt, and
everything will sort of work.

The e1000_irq() routine should (per mcb30) do enable on non-zero,
disable on zero.  This is not consistent in all drivers, so I'll
wait to update it when doing a global sweep.

This needs to be done manually because if the irq() routine is
implemented then we want something like "nic->irqno = pci->irqno;",
else we do "nic->irqno = 0;" nic->ioaddr may also need to be set
carefully.

Also added local variables to end of many files, for emacs indentation
to match kernel style (tab does 8 space indent).

Cleanups for e1000.c.

I have successfully booted DOS via iSCSI and PXELINUX via TFTP with this
version of the e1000 driver.

There may still be an issue with memory handling, since it seems to
die ungracefully when ARP packets come in after loading a kernel.
Something to debug.

autonegotiation still needs work.  receive is not working yet.

any rewrite.

DBG_PRINTF() and assert().

crash the machine.

tracking down a bug that turned out to be a free_iob() used where I
needed a netdev_tx_complete().  This left the freed I/O buffer on the
net device's TX list, with bad, bad consequences later.

Also fixed the bug in question.