genirq: Make irq_set_vcpu_affinity available for CONFIG_SMP=n

irq_set_vcpu_affinity() is needed when CONFIG_SMP=n, so move the
definition out of "#ifdef CONFIG_SMP"

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Feng Wu <feng.wu@intel.com>
Cc: jiang.liu@linux.intel.com
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1443860438-144926-1-git-send-email-feng.wu@intel.com


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