tc: make tc_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 tc_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>
Acked-by: Maciej W. Rozycki <macro@orcam.me.uk>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

drivers/tc/tc-driver.c

@@ -95,7 +95,7 @@ static int tc_bus_match(struct device *dev, struct device_driver *drv)
 	return 0;
 }
 
-struct bus_type tc_bus_type = {
+const struct bus_type tc_bus_type = {
 	.name	= "tc",
 	.match	= tc_bus_match,
 };

include/linux/tc.h

@@ -120,7 +120,7 @@ static inline unsigned long tc_get_speed(struct tc_bus *tbus)
 
 #ifdef CONFIG_TC
 
-extern struct bus_type tc_bus_type;
+extern const struct bus_type tc_bus_type;
 
 extern int tc_register_driver(struct tc_driver *tdrv);
 extern void tc_unregister_driver(struct tc_driver *tdrv);