soundwire: bus_type: make sdw_bus_type const

Since commit d492cc2 ("driver core: device.h: make struct
bus_type a const *"), the driver core can properly handle constant
struct bus_type, move the sdw_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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240213-bus_cleanup-soundwire-v1-1-3878b00f6f57@marliere.net
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: rbmarliere

drivers/soundwire/bus_type.c

@@ -72,7 +72,7 @@ int sdw_slave_uevent(const struct device *dev, struct kobj_uevent_env *env)
 	return 0;
 }
 
-struct bus_type sdw_bus_type = {
+const struct bus_type sdw_bus_type = {
 	.name = "soundwire",
 	.match = sdw_bus_match,
 };

include/linux/soundwire/sdw_type.h

@@ -4,7 +4,7 @@
 #ifndef __SOUNDWIRE_TYPES_H
 #define __SOUNDWIRE_TYPES_H
 
-extern struct bus_type sdw_bus_type;
+extern const struct bus_type sdw_bus_type;
 extern struct device_type sdw_slave_type;
 extern struct device_type sdw_master_type;