Support a shadowed ROM when running with an ACPI capable PROM.

Define a new dev.resource flag IORESOURCE_ROM_BIOS_COPY to
describe the case of a BIOS shadowed ROM, which can then
be used to avoid pci_map_rom() making an unneeded call to
pci_enable_rom().
Signed-off-by: John Keller <jpk@sgi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>