x86: add apic probe for genapic 64bit - fix

intr_remapping_enabled get assigned later, so need to check that
in setup_apic_routing

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>