x86, x2apic: Move the common bits to x2apic.h

To eliminate code duplication.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: steiner@sgi.com
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/20110519234637.591426753@sbsiddha-MOBL3.sc.intel.com


Signed-off-by: Ingo Molnar <mingo@elte.hu>