[efi] Add definitions of GUIDs observed during Windows boot

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Dump details of any calls to our dummy block and disk I/O protocols

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[romprefix] Do not preserve unused register %di

Since some PnP BIOSes fail to set %es:di to point to the PnP signature
on entry, we identify a PnP BIOS by scanning through the top 64kB of
base memory looking for the PnP structure.  We therefore don't
actually use the values of %es:di provided to the initialisation entry
point, and so there is no need to preserve them.

Signed-off-by: Michael Brown <mcb30@ipxe.org>