[IA64] pvops: define initialization hooks, pv_init_ops, for paravirtualized environment.

define pv_init_ops hooks which represents various initialization
hooks for paravirtualized environment. and add hooks.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>