x86, apic: Use probe routines to simplify apic selection

Use the unused probe routine in the apic driver to finalize the
apic model selection. This cleans up the
default_setup_apic_routing() and this probe routine in future
can also be used for doing any apic model specific
initialisation.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: steiner@sgi.com
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/20110519234637.247458931@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>