tpm/tpm_ftpm_tee: Make use of tee specific driver registration

tpm/tpm_ftpm_tee: Make use of tee specific driver registration

tee_client_driver_register() is typed more strongly and cares about
assigning the driver's bus. Similar for tee_client_driver_unregister().

Make use of these functions.

Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>