mm: cma: 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.

Link: https://lkml.kernel.org/r/20230220-kobj_type-mm-cma-v1-1-45996cff1a81@weissschuh.netSigned-off-by: Thomas Weißschuh <linux@weissschuh.net>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/cma_sysfs.c

@@ -64,7 +64,7 @@ static struct attribute *cma_attrs[] = {
 };
 ATTRIBUTE_GROUPS(cma);
 
-static struct kobj_type cma_ktype = {
+static const struct kobj_type cma_ktype = {
 	.release = cma_kobj_release,
 	.sysfs_ops = &kobj_sysfs_ops,
 	.default_groups = cma_groups,