Move TPM passthrough specific command line options to backend structure

Move the TPM passthrough specific command line options to the passthrough
backend implementation and attach them to the backend's interface structure.

Add code to tpm.c for validating the TPM command line options.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Corey Bryan <coreyb@linux.vnet.ibm.com>
Message-id: 1366641699-21420-1-git-send-email-stefanb@linux.vnet.ibm.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
