x86, irq: Provide empty send_cleanup_vector() stub for UP builds

Define an empty send_cleanup_vector() for UP kernel to fix link error
of undefined reference, which is used by uv_irq and irq_remapping.

[ tglx: Made it an inline stub and moved it ahead of the file split
  	changes ]
Signed-off-by: NJiang Liu <jiang.liu@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1414397531-28254-21-git-send-email-jiang.liu@linux.intel.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/hw_irq.h

@@ -153,7 +153,11 @@ struct irq_cfg {
 };
 
 extern int assign_irq_vector(int, struct irq_cfg *, const struct cpumask *);
+#ifdef CONFIG_SMP
 extern void send_cleanup_vector(struct irq_cfg *);
+#else
+static inline void send_cleanup_vector(struct irq_cfg *c) { }
+#endif
 
 struct irq_data;
 int __ioapic_set_affinity(struct irq_data *, const struct cpumask *,