kdoc for tpm2_flush_context_cmd() was off.

Fixes: 9aa36b39 ("tpm: export tpm2_flush_context_cmd")'
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>