const_structs.checkpatch: add bus_type

Since commit d492cc25 ("driver core: device.h: make struct bus_type a
const *"), the driver core can properly handle constant struct bus_type. 
Make sure that new usages of the struct already enter the tree as const.

Link: https://lkml.kernel.org/r/20240204-bus_cleanup-checkpatch-v1-1-8d51dcecda20@marliere.netSigned-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Suggested-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/const_structs.checkpatch

@@ -2,6 +2,7 @@ acpi_dock_ops
 address_space_operations
 backlight_ops
 block_device_operations
+bus_type
 clk_ops
 comedi_lrange
 component_ops