genirq/irqdesc: Make kobj_type structures constant

Since commit ee6d3dd4 ("driver core: make kobj_type constant.")
the driver core allows the usage of const struct kobj_type.

Take advantage of this to constify the structure definitions which prevents
modification at runtime.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230217-kobj_type-irq-v1-1-fedfacaf8cdb@weissschuh.net

kernel/irq/irqdesc.c

@@ -277,7 +277,7 @@ static struct attribute *irq_attrs[] = {
 };
 ATTRIBUTE_GROUPS(irq);
 
-static struct kobj_type irq_kobj_type = {
+static const struct kobj_type irq_kobj_type = {
 	.release	= irq_kobj_release,
 	.sysfs_ops	= &kobj_sysfs_ops,
 	.default_groups = irq_groups,
@@ -335,7 +335,7 @@ postcore_initcall(irq_sysfs_init);
 
 #else /* !CONFIG_SYSFS */
 
-static struct kobj_type irq_kobj_type = {
+static const struct kobj_type irq_kobj_type = {
 	.release	= irq_kobj_release,
 };