firewire: make fw_bus_type const

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

Cc: Takashi Sakamoto <[e-mail]>
Cc: [e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>
Link: https://lore.kernel.org/r/2023121931-skydiver-dodgy-d1bd@gregkh
Signed-off-by: Takashi Sakamoto <[e-mail]>

drivers/firewire/core-device.c

···
 	return 0;
 }
 
-struct bus_type fw_bus_type = {
+const struct bus_type fw_bus_type = {
 	.name = "firewire",
 	.match = fw_unit_match,
 	.probe = fw_unit_probe,

include/linux/firewire.h

···
 int fw_csr_iterator_next(struct fw_csr_iterator *ci, int *key, int *value);
 int fw_csr_string(const u32 *directory, int key, char *buf, size_t size);
 
-extern struct bus_type fw_bus_type;
+extern const struct bus_type fw_bus_type;
 
 struct fw_card_driver;
 struct fw_node;