eepro100: Support gpxe boot for all eepro100 devices

eepro100: Support gpxe boot for all eepro100 devices

Only two boot ROM files are needed for all devices.

* Add these GPXE ROM files using new naming convention
  (as discussed on qemu-devel). Both files were created
  with http://rom-o-matic.net/, PCI vendor / device ids
  as in ROM filenames and option BANNER_TIMEOUT = 0.

* Remove old PXE ROM file for i82559er.
  It was replaced by gpxe-eepro100-80861209.rom.

* Update pc-bios/README (and sort entries).

Full support still needs additional eepro100 fixes.

Signed-off-by: Stefan Weil <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>