kvm,async_pf: Use swq_has_sleeper()

... as we've got the new helper now. This caller already
does the right thing, hence no changes in semantics.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

virt/kvm/async_pf.c

@@ -106,11 +106,7 @@ static void async_pf_execute(struct work_struct *work)
 
 	trace_kvm_async_pf_completed(addr, gva);
 
-	/*
-	 * This memory barrier pairs with prepare_to_wait's set_current_state()
-	 */
-	smp_mb();
-	if (swait_active(&vcpu->wq))
+	if (swq_has_sleeper(&vcpu->wq))
 		swake_up(&vcpu->wq);
 
 	mmput(mm);