xen: pcpu: make xen_pcpu_subsys const

Now that the driver core can properly handle constant struct bus_type,
move the xen_pcpu_subsys 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 <[email protected]>
Suggested-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Ricardo B. Marliere <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Juergen Gross <[email protected]>

Author: rbmarliere

drivers/xen/pcpu.c

@@ -65,7 +65,7 @@ struct pcpu {
 	uint32_t flags;
 };
 
-static struct bus_type xen_pcpu_subsys = {
+static const struct bus_type xen_pcpu_subsys = {
 	.name = "xen_cpu",
 	.dev_name = "xen_cpu",
 };