x86, ipi: Clean up safe_smp_processor_id() by using the cpu_has_apic() macro helper

We already use a lot of cpu_has_ helpers.
Lets do here the same for consistency.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <20090705160154.GB4791@lenovo>
Signed-off-by: Ingo Molnar <mingo@elte.hu>