KVM: s390: use kvm_vcpu_on_spin for diag 0x44

Lets replace the old open coded version of diag 0x44 (which relied on
compat_sched_yield) with kvm_vcpu_on_spin.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/s390/kvm/diag.c

@@ -47,9 +47,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
 {
 	VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
 	vcpu->stat.diagnose_44++;
-	vcpu_put(vcpu);
-	yield();
-	vcpu_load(vcpu);
+	kvm_vcpu_on_spin(vcpu);
 	return 0;
 }