[IA64] pvops: introduce pv_cpu_ops to paravirtualize privileged instructions.

introduce pv_cpu_ops to paravirtualize privleged instructions
which are defined by ia64 intrinsics.
make them indirect C function calls by introducing function
tables, pv_cpu_ops.

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