x86/apic: Sanitize ioapic handling

We have proper stubs for the IOAPIC=n case and the setup/enable
function have the required checks inside now. Remove the ifdeffery and
the copy&pasted conditionals.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de&gt;C>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/20150115211703.569830549@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>