KVM: s390: Privileged operation check for TPROT

TPROT is a privileged instruction and thus should generate a privileged
operation exception when the problem state bit is not cleared in the PSW.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>