Input: synaptics-rmi4 - make rmi_bus_type const

Now that the driver core can properly handle constant struct bus_type,
move the variable rmi_bus_type to be a constant structure as well,
placing it into read-only memory which can not be modified at runtime.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240210-bus_cleanup-input2-v1-1-0daef7e034e0@marliere.net
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: rbmarliere

drivers/input/rmi4/rmi_bus.c

@@ -344,7 +344,7 @@ static int rmi_bus_match(struct device *dev, struct device_driver *drv)
 	return physical || rmi_function_match(dev, drv);
 }
 
-struct bus_type rmi_bus_type = {
+const struct bus_type rmi_bus_type = {
 	.match		= rmi_bus_match,
 	.name		= "rmi4",
 };

drivers/input/rmi4/rmi_bus.h

@@ -185,7 +185,7 @@ static inline int rmi_write_block(struct rmi_device *d, u16 addr,
 
 int rmi_for_each_dev(void *data, int (*func)(struct device *dev, void *data));
 
-extern struct bus_type rmi_bus_type;
+extern const struct bus_type rmi_bus_type;
 
 int rmi_of_property_read_u32(struct device *dev, u32 *result,
 				const char *prop, bool optional);