[IA64] xencomm: add PHYSDEVOP_pirq_eoi_gmfn support.

[IA64] xencomm: add PHYSDEVOP_pirq_eoi_gmfn support.

This patch fixes some weird issues in upstream.
Dom0 uses one page shared with hypervisor to notify which pirqs need EOI
writes, but the page is set incorrectly for ia64 due to following reasons:
1. the related two hypercalls are not enabled in the correct way, so this page
is not really used by dom0 and hypervisor do nothing when dom0 writes eoi.

Signed-off-by : Xiantao Zhang <xiantao.zhang@intel.com>