x86, apic: use pr_ macro

Replace recenly appeared printk with pr_ macro
(the file already use a lot of them).

[ Impact: cleanup ]

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
LKML-Reference: <20090501195425.GB4633@lenovo>
Signed-off-by: Ingo Molnar <mingo@elte.hu>