tpm/tpm_ftpm_tee: add shutdown call back

Add shutdown call back to close existing session with fTPM TA
to support kexec scenario.

Add parentheses to function names in comments as specified in kdoc.

Signed-off-by: Thirupathaiah Annapureddy <thiruan@microsoft.com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>