x86: untable __init references between IO data

Earlier patch added IO APIC setup into local APIC setup. This caused
modpost warnings. Fix them by untangling setup_local_APIC() and splitting
it into smaller functions. The IO APIC initialization is only called
for the BP init.

Also removed some outdated debugging code and minor cleanup.

[ tglx: arch/x86 adaptation ]

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>