tee: add ARM_SMCCC dependency

For the moment, the tee subsystem only makes sense in combination with
the op-tee driver that depends on ARM_SMCCC, so let's hide the subsystem
from users that can't select that.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/tee/Kconfig

 # Generic Trusted Execution Environment Configuration
 config TEE
 	tristate "Trusted Execution Environment support"
+	depends on HAVE_ARM_SMCCC || COMPILE_TEST
 	select DMA_SHARED_BUFFER
 	select GENERIC_ALLOCATOR
 	help