[IA64] Handle MMIO EFI mappings outside the page table range

[IA64] Handle MMIO EFI mappings outside the page table range

We cannot rely on MMIO pages presented in the EFI mem-map can be
mapped directly to the same meta-physical address, because of
restrictions on the address range imposed by the page tables.

As an example, IO ports are located at 0x1ffffffffc000000 on many SN2
systems.

Change assign_domain_mmio_page() to take a flags and a source and
destination address to handle this and catch IO ports above
0x1ffffffff0000000 and map them down to a safe area.

Signed-off-by: Jes Sorensen <jes@sgi.com>