KVM: x86: Avoid using plain integer as NULL pointer warning

This patch fix the following sparse warning:

for file arch/x86/kvm/x86.c:
warning: Using plain integer as NULL pointer
Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

@@ -5919,7 +5919,7 @@ static void kvm_pv_kick_cpu_op(struct kvm *kvm, unsigned long flags, int apicid)
 	lapic_irq.dest_id = apicid;
 
 	lapic_irq.delivery_mode = APIC_DM_REMRD;
-	kvm_irq_delivery_to_apic(kvm, 0, &lapic_irq, NULL);
+	kvm_irq_delivery_to_apic(kvm, NULL, &lapic_irq, NULL);
 }
 
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)