siox: constify the struct device_type usage

Since commit aed65af1 ("drivers: make device_type const"), the driver
core can properly handle constant struct device_type. Move the
siox_device_type and siox_master_type variables to be constant structures
as well, placing it into read-only memory which can not be modified at
runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Thorsten Scherer <t.scherer@eckelmann.de>
Link: https://lore.kernel.org/r/20240219-device_cleanup-siox-v1-1-eb32ca2b0113@marliere.netSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/siox/siox-core.c

@@ -498,7 +498,7 @@ static void siox_device_release(struct device *dev)
 	kfree(sdevice);
 }
 
-static struct device_type siox_device_type = {
+static const struct device_type siox_device_type = {
 	.groups = siox_device_groups,
 	.release = siox_device_release,
 };
@@ -676,7 +676,7 @@ static void siox_master_release(struct device *dev)
 	kfree(smaster);
 }
 
-static struct device_type siox_master_type = {
+static const struct device_type siox_master_type = {
 	.groups = siox_master_groups,
 	.release = siox_master_release,
 };