kvm: fix warning for CONFIG_HAVE_KVM_EVENTFD builds

Move the kvm_arch_irq_routing_update() prototype outside of
ifdef CONFIG_HAVE_KVM_EVENTFD guards to fix the following sparse warning:

arch/s390/kvm/../../../virt/kvm/irqchip.c:171:28: warning: symbol 'kvm_arch_irq_routing_update' was not declared. Should it be static?
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/linux/kvm_host.h

@@ -1105,7 +1105,6 @@ static inline void kvm_irq_routing_update(struct kvm *kvm)
 {
 }
 #endif
-void kvm_arch_irq_routing_update(struct kvm *kvm);
 
 static inline int kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 {
@@ -1114,6 +1113,8 @@ static inline int kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 
 #endif /* CONFIG_HAVE_KVM_EVENTFD */
 
+void kvm_arch_irq_routing_update(struct kvm *kvm);
+
 static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
 {
 	/*