[coreboot] [PATCH]Improve YABEL compatibility

[Patrick Georgi]

Hi,

attached patch improves compatibility of YABEL with realmode execution
of the VGA BIOS by passing through access to IVT, BDA and option ROM
area directly, instead of copying them from the emulated memory to real
memory after initialization is done.

Some VGA BIOSes seem to map hardware registers into the option ROM area,
so routing accesses to these into emulated RAM will lead to all kinds of
unexpected behaviour.

The intent of YABEL in coreboot is to provide improved security by
isolating hardware access - this patch doesn't improve or degrade
security as the memory regions in question were already copied back
after emulation before this patch.

Signed-off-by: Patrick Georgi