tpm: Add HMAC session start and end functions

Add session  based HMAC  authentication plus parameter  decryption and
response encryption  using AES. The  basic design is to  segregate all
the nasty crypto, hash and hmac code into tpm2-sessions.c and export a
usable API.  The API first of all starts off by gaining a session with
tpm2_start_auth_session() which  initiates a session with  the TPM and
allocates  an  opaque  tpm2_auth   structure  to  handle  the  session
parameters.  The  design is that  session use will be  single threaded
from start to finish under the ops lock, so the tpm2_auth structure is
stored in struct tpm2_chip to simpify the externally visible API.

The session can be ended with tpm2_end_auth_session() which is
designed only to be used in error legs.  Ordinarily the further
session API (future patches) will end or continue the session
appropriately without having to call this.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> # crypto API parts
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>