x86/apic: Remove unused function prototypes

Some function prototypes declared in asm/apic.h are never
defined, so remove them.

Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1402042354210.7839@chino.kir.corp.google.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>