[romprefix] Report a pessimistic runtime size estimate

PCI3.0 allows us to report a "runtime size" which can be smaller than
the actual ROM size.  On systems that support PMM our runtime size
will be small (~2.5kB), which helps to conserve the limited option ROM
space.  However, there is no guarantee that the PMM allocation will
succeed, and so we need to report the worst-case runtime size in the
PCI header.

Move the "shrunk ROM size" field from the PCI header to a new "iPXE
ROM header", allowing it to be accessed by ROM-manipulation utilities
such as disrom.pl.

Reported-by: Anton D. Kachalov <mouse@yandex-team.ru>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/util/fixrom.pl

@@ -32,6 +32,7 @@ foreach my $romfile ( @romfiles ) {
   my $image = $rom;
   while ( $image ) {
     $image->pnp_header->fix_checksum() if $image->pnp_header;
+    $image->ipxe_header->fix_checksum() if $image->ipxe_header;
     $image->fix_checksum();
     $image = $image->next_image();
   }