scsi: target: tcm_loop: Make tcm_loop_lld_bus const

Now that the driver core can properly handle constant struct bus_type, move
the tcm_loop_lld_bus 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>
Link: https://lore.kernel.org/r/20240204-bus_cleanup-target-v1-1-96106936c4ab@marliere.netReviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/loopback/tcm_loop.c

@@ -83,7 +83,7 @@ static int tcm_loop_show_info(struct seq_file *m, struct Scsi_Host *host)
 static int tcm_loop_driver_probe(struct device *);
 static void tcm_loop_driver_remove(struct device *);
 
-static struct bus_type tcm_loop_lld_bus = {
+static const struct bus_type tcm_loop_lld_bus = {
 	.name			= "tcm_loop_bus",
 	.probe			= tcm_loop_driver_probe,
 	.remove			= tcm_loop_driver_remove,