[IA64] fix XENMEM_add_to_physmap with XENMAPSPACE_mfn.

[IA64] fix XENMEM_add_to_physmap with XENMAPSPACE_mfn.

This patch fixes HVM domain save/restore.
Tools stack is aware of where memory is populated in guest domain.
But XENMEM_add_to_physmap with XENMAPSPACE_mfn doesn't update
the information related to guest memory map. So guest domain
save/dump-core fails to dump pages which were added by the hypercall.

This patch makes the hypercall update the memory map information
of a given guest domain.
This introduces the race between writers and readers of
the info. Later a new hypercall will be introduced to get memmap
from the guest with lock which prevents this race.
Even if the tools stack can get the memmap by foreign
domain page mapping, it should get memmap by the
newly added hypercall which will be added later.

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