ia64/pv_ops/xen: define xen paravirtualized instructions for hand wri…

…tten assembly code

define xen paravirtualized instructions for hand written assembly code.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Cc: Akio Takebe <takebe_akio@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>