kvm/s390: drop unpaired smp_mb

smp_mb on vcpu destroy isn't paired with anything, violating pairing
rules, and seems to be useless.

Drop it.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <1452010811-25486-1-git-send-email-mst@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/kvm-s390.c

@@ -1221,7 +1221,6 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 	kvm_clear_async_pf_completion_queue(vcpu);
 	if (!kvm_is_ucontrol(vcpu->kvm))
 		sca_del_vcpu(vcpu);
-	smp_mb();
 
 	if (kvm_is_ucontrol(vcpu->kvm))
 		gmap_free(vcpu->arch.gmap);