EDAC: constantify the struct bus_type usage

In many places in the edac code, struct bus_type pointers are passed
around and then eventually sent to the driver core, which can handle a
constant pointer. So constantify all of the edac usage of these as well
because the data in them is never modified by the edac code either.

Cc: Borislav Petkov <[e-mail]>
Cc: Tony Luck <[e-mail]>
Cc: James Morse <[e-mail]>
Cc: Mauro Carvalho Chehab <[e-mail]>
Cc: Robert Richter <[e-mail]>
Cc: <[e-mail]>
Link: https://lore.kernel.org/r/2023121909-tribute-punctuate-4b22@gregkh
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/edac/edac_device.h

···
 	struct edac_dev_sysfs_attribute *sysfs_attributes;
 
 	/* pointer to main 'edac' subsys in sysfs */
-	struct bus_type *edac_subsys;
+	const struct bus_type *edac_subsys;
 
 	/* the internal state of this controller instance */
 	int op_state;

drivers/edac/edac_device_sysfs.c

···
 int edac_device_register_sysfs_main_kobj(struct edac_device_ctl_info *edac_dev)
 {
 	struct device *dev_root;
-	struct bus_type *edac_subsys;
+	const struct bus_type *edac_subsys;
 	int err = -ENODEV;
 
 	edac_dbg(1, "\n");

drivers/edac/edac_module.c

···
  * sysfs object: /sys/devices/system/edac
  *	need to export to other files
  */
-static struct bus_type edac_subsys = {
+static const struct bus_type edac_subsys = {
 	.name = "edac",
 	.dev_name = "edac",
 };
···
 }
 
 /* return pointer to the 'edac' node in sysfs */
-struct bus_type *edac_get_sysfs_subsys(void)
+const struct bus_type *edac_get_sysfs_subsys(void)
 {
 	return &edac_subsys;
 }

drivers/edac/edac_pci_sysfs.c

···
 static int edac_pci_main_kobj_setup(void)
 {
 	int err = -ENODEV;
-	struct bus_type *edac_subsys;
+	const struct bus_type *edac_subsys;
 	struct device *dev_root;
 
 	edac_dbg(0, "\n");

include/linux/edac.h

···
 
 extern int edac_op_state;
 
-struct bus_type *edac_get_sysfs_subsys(void);
+const struct bus_type *edac_get_sysfs_subsys(void);
 
 static inline void opstate_init(void)
 {
···
  */
 struct mem_ctl_info {
 	struct device			dev;
-	struct bus_type			*bus;
+	const struct bus_type		*bus;
 
 	struct list_head link;	/* for global list of mem_ctl_info structs */