coresight: make coresight_bustype const

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

Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/2024010531-tinfoil-avert-4a57@gregkh

drivers/hwtracing/coresight/coresight-core.c

@@ -1799,7 +1799,7 @@ char *coresight_alloc_device_name(struct coresight_dev_list *dict,
 }
 EXPORT_SYMBOL_GPL(coresight_alloc_device_name);
 
-struct bus_type coresight_bustype = {
+const struct bus_type coresight_bustype = {
 	.name	= "coresight",
 };
 

include/linux/coresight.h

@@ -35,7 +35,7 @@
 
 #define CORESIGHT_UNLOCK	0xc5acce55
 
-extern struct bus_type coresight_bustype;
+extern const struct bus_type coresight_bustype;
 
 enum coresight_dev_type {
 	CORESIGHT_DEV_TYPE_SINK,