libtpmtss: Establish session with TPM 2.0

libtpmtss: Establish session with TPM 2.0

Using the trusted RSA or ECC Endorsement Key of the TPM 2.0 a
secure session is established via RSA public key encryption or
an ephemeral ECDH key exchange, respectively.

The session allows HMAC-based authenticated communication with
the TPM 2.0 and the exchanged parameters can be encrypted where
necessary to guarantee confidentiality.