The Linux sandalfoot zImage has an initialisation process which resets the
VGA controller by setting all the BAR addresses to zero to access the VGA
ioports at their legacy addresses.

Unfortunately setting the framebuffer BAR to address 0 makes the framebuffer
memory overlap the internal VGA memory causing accesses to fail, and so
prevents the kernel from switching successfully to text mode.

Since OpenHackWare configures the framebuffer BAR address outside of the legacy
VGA internal memory space, remove pci_allow_0_address from the 40p machine class
which causes the BAR reprogramming to zero to fail and so the VGA internal
memory can be accessed correctly again.
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>