x86, ioapic: Consolidate the explicit EOI code

Consolidate the io-apic EOI code in clear_IO_APIC_pin() and
eoi_ioapic_irq().

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Rafael Wysocki <rjw@novell.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: lchiquitto@novell.com
Cc: jbeulich@novell.com
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/20110825190657.259696697@sbsiddha-desk.sc.intel.com


Signed-off-by: Ingo Molnar <mingo@elte.hu>