stubdom/vtpm: Support locality field

stubdom/vtpm: Support locality field

The vTPM protocol now contains a field allowing the locality of a
command to be specified; pass this to the TPM when processing a packet.
While the locality is not currently checked for validity, a binding
between locality and some distinguishing feature of the client domain
(such as the XSM label) will need to be defined in order to properly
support a multi-client vTPM.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Matthew Fioravante <matthew.fioravante@jhuapl.edu>