Print only once that the system is supporting x2apic mode.

Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
LKML-Reference: <4B226E92.5080904@sgi.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>