radeonfb was HPMC-ing my C8000 by trying to map its expansion rom from
IO_VIEW, instead of PA_VIEW. Fix seems to be to ensure that its disabled
ROM is properly inserted into the resource tree.

FIXME: this will result in a whinging printk for cards which share expansion
ROMS, such as a quad tulip. Thankfully, it isn't harmful.
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>