You could try having SeaBIOS enable your ROM. There have been
several
cases
where SeaBIOS was less picky than the others.
I forgot to mention that also tried seabios without success.
I attached a log file for seabios.
I don't see the lines setting the VGA bridge bits.
It should say something like "Allocating VGA resource PCI 3:00.0" and then list the bridges.
Is your log level debug? Do you have CONFIG_CONSOLE_VGA set?
Thanks, Myles