The TPM1.2 PCR Extend operation only returns 20 bytes in the body,
which is the size of the PCR state.

This fixes a problem where IMA gets errors with every PCR Extend.

Fixes: c659af78 ("tpm: Check size of response before accessing data")
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>