The userpace expects to read the number of bytes stated in the header.
Returning the size of the buffer instead would be unexpected.

Cc: stable@vger.kernel.org
Fixes: 095531f8 ("tpm: return a TPM_RC_COMMAND_CODE response if command is not implemented")
Signed-off-by: NRicardo Schwarzmeier <Ricardo.Schwarzmeier@infineon.com>
Reviewed-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>