tee: combine "config" and "menu" for TEE's menuconfig

Don't let TEE occupy two lines in menuconfig when practically no
other (sub)menu does either.

Signed-off-by: Jan Engelhardt <jengelh@inai.de>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>