raven: Set a correct PCI memory region

PCI memory region is 0x3f000000 bytes starting at 0xc0000000.

However, keep compatibility with Open Hack'Ware expectations
by adding a hack for Open Hack'Ware display.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Andreas Färber <andreas.faerber@web.de>
