x86/ioapic: Provide stub functions for IOAPIC%3Dn

To avoid lots of ifdeffery provide proper stubs for setup_IO_APIC(),
enable_IO_APIC() and setup_ioapic_dest().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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/20150115211703.397170414@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/io_apic.h

@@ -279,6 +279,11 @@ static inline void disable_ioapic_support(void) { }
 #define native_ioapic_set_affinity	NULL
 #define native_setup_ioapic_entry	NULL
 #define native_eoi_ioapic_pin		NULL
+
+static inline void setup_IO_APIC(void) { }
+static inline void enable_IO_APIC(void) { }
+static inline void setup_ioapic_dest(void) { }
+
 #endif
 
 #endif /* _ASM_X86_IO_APIC_H */