Commit d2add27c ("tpm: Add NULL primary creation") introduced
CONFIG_TCG_TPM2_HMAC. When this option is enabled on ppc64 then the
following message appears in the kernel log due to a missing call to
tpm2_sessions_init().

[    2.654549] tpm tpm0: auth session is not active

Add the missing call to tpm2_session_init() to the ibmvtpm driver to
resolve this issue.

Cc: stable@vger.kernel.org # v6.10+
Fixes: d2add27c ("tpm: Add NULL primary creation")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>