cpufreq: Make kobj_type structure 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 definition to prevent
modification at runtime.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -993,7 +993,7 @@ static const struct sysfs_ops sysfs_ops = {
 	.store	= store,
 };
 
-static struct kobj_type ktype_cpufreq = {
+static const struct kobj_type ktype_cpufreq = {
 	.sysfs_ops	= &sysfs_ops,
 	.default_groups	= cpufreq_groups,
 	.release	= cpufreq_sysfs_release,