tee: make tee_bus_type const

Since commit d492cc25 ("driver core: device.h: make struct
bus_type a const *"), the driver core can properly handle constant
struct bus_type, move the tee_bus_type variable to be a constant
structure as well, placing it into read-only memory which can not be
modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/tee/tee_core.c

@@ -1226,7 +1226,7 @@ static int tee_client_device_uevent(const struct device *dev,
 	return add_uevent_var(env, "MODALIAS=tee:%pUb", dev_id);
 }
 
-struct bus_type tee_bus_type = {
+const struct bus_type tee_bus_type = {
 	.name		= "tee",
 	.match		= tee_client_device_match,
 	.uevent		= tee_client_device_uevent,

include/linux/tee_drv.h

@@ -482,7 +482,7 @@ static inline bool tee_param_is_memref(struct tee_param *param)
 	}
 }
 
-extern struct bus_type tee_bus_type;
+extern const struct bus_type tee_bus_type;
 
 /**
  * struct tee_client_device - tee based device