piix: fix 32bit pci hole

piix: fix 32bit pci hole

Make the 32bit pci hole start at end of ram, so all possible address
space is covered.

We used to try and make addresses aligned so they are easier to cover
with MTRRs, but since they are cosmetic on KVM, this is probably not
worth worrying about.
Of course the firmware can use less than that.  Leaving space unused is
no problem, mapping pci bars outside the hole causes problems though.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>