KVM: s390: reset crypto attributes for all vcpus

Introduces a new function to reset the crypto attributes for all
vcpus whether they are running or not. Each vcpu in KVM will
be removed from SIE prior to resetting the crypto attributes in its
SIE state description. After all vcpus have had their crypto attributes
reset the vcpus will be restored to SIE.

This function is incorporated into the kvm_s390_vm_set_crypto(kvm)
function to fix a reported issue whereby the crypto key wrapping
attributes could potentially get out of synch for running vcpus.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reported-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>