x86, ioapic: Define irq_remap_modify_chip_defaults()

Define irq_remap_modify_chip_defaults() and remove the duplicate
code, cleanup the unnecessary ifdefs.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: yinghai@kernel.org
Cc: youquan.song@intel.com
Cc: joerg.roedel@amd.com
Cc: tony.luck@intel.com
Cc: dwmw2@infradead.org
Link: http://lkml.kernel.org/r/20110824001456.499225692@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>