x86/apic: Replace io_apic_ops with x86_io_apic_ops.

Which makes the code fit within the rest of the x86_ops functions.

Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
[v1: Changed x86_apic -> x86_ioapic per Yinghai Lu <yinghai@kernel.org> suggestion]
[v2: Rebased on tip/x86/urgent and redid to match Ingo's syntax style]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>