[IA64] Allocate frame table/mpt table at mfn=0

[IA64] Allocate frame table/mpt table at mfn=0

Allocate frame table/mpt table at mfn=0 even when memory isn't assigned at
mfn=0 as work around for transate_domain_pte().

transate_domain_pte() returns mfn=0 when the machine page isn't present
as a work around for memory mapped I/O where no device is assigned.
Xen might access page_info of mfn=0, so it must be guaranteed that it
exists. Otherwise xen panics with a tlb miss fault in xen's virtual
address area.

Once transate_domain_pte() is fixed correctly, this will be removed.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>