fsi: make fsi_bus_type constant

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

Cc: Ninad Palsule <ninad@linux.ibm.com>
Cc: linux-fsi@lists.ozlabs.org
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/2025070100-overblown-busily-a04b@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: gregkh

drivers/fsi/fsi-core.c

@@ -1404,7 +1404,7 @@ void fsi_driver_unregister(struct fsi_driver *fsi_drv)
 }
 EXPORT_SYMBOL_GPL(fsi_driver_unregister);
 
-struct bus_type fsi_bus_type = {
+const struct bus_type fsi_bus_type = {
 	.name		= "fsi",
 	.match		= fsi_bus_match,
 };

include/linux/fsi.h

@@ -68,7 +68,7 @@ extern int fsi_slave_read(struct fsi_slave *slave, uint32_t addr,
 extern int fsi_slave_write(struct fsi_slave *slave, uint32_t addr,
 		const void *val, size_t size);
 
-extern struct bus_type fsi_bus_type;
+extern const struct bus_type fsi_bus_type;
 extern const struct device_type fsi_cdev_type;
 
 enum fsi_dev_type {