Store the TPM interface, the actual object may be different from
TPMState. Keep a reference on the interface, and check the backend
wasn't already initialized.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>