[coreboot] PCI BIOS Extension ROM in v3

[Myles Watson]

Coreboot v3 refuses to initialize the VGA in QEMU because the PCI device
ID's are mismatched.

It turns out that the header has been overwritten by a copyright string, so
that v3 is following a bad pointer into the ROM looking for the PCI device
IDs and not finding it.  Coreboot v2 still successfully initializes the VGA
because it skips the vendor check.

The question is if we should make the vendor check a warning instead of
failing.  I realize that the right thing to do is fix the ROM, but there may
be other broken ROMs as well.

Another thing we could do is only fail on a mismatched ID if we find a
correct PCIR signature on the data section.

Myles