We need to unlock the kvm->lock mutex in the error case.

Reported-by: smatch
Fixes: 37940fb0 ("KVM: s390: device attrs to enable/disable AP interpretation")
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NJanosch Frank <frankja@linux.ibm.com>
Reviewed-by: NPierre Morel <pmorel@linux.ibm.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>