tss2: Add TPM2 buffer handling functions

tss2: Add TPM2 buffer handling functions

As the preparation to support TPM2 Software Stack (TSS2), this commit
implements the TPM2 buffer handling functions to pack data for the TPM2
commands and unpack the data from the response.

Cc: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Hernan Gatta <hegatta@linux.microsoft.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>