x86, apic: Clean up bigsmp apic selection code

Make generic_bigsmp_probe() return struct apic *. This will
avoid exporting apic_bigsmp, which will be consistent with
others.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: steiner@sgi.com
Cc: gorcunov@openvz.org
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/20110521005526.252703851@sbsiddha-MOBL3.sc.intel.com


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