tpm/tpm_ftpm_tee: Fix error handling in ftpm_mod_init()

The ftpm_mod_init() returns the driver_register() directly without checking
its return value, if driver_register() failed, the ftpm_tee_plat_driver is
not unregistered.

Fix by unregister ftpm_tee_plat_driver when driver_register() failed.

Fixes: 9f1944c2 ("tpm_ftpm_tee: register driver on TEE bus")
Signed-off-by: Yuan Can <yuancan@huawei.com>
Reviewed-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>