powerpc: pseries: Constify struct kobj_type

'struct kobj_type' is not modified. It is only used in kobject_init()
which takes a 'const struct kobj_type *ktype' parameter.

Constifying this structure moves some data to a read-only section,
so increase over all security.

On a x86_64, compiled with ppc64 defconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
   1885	    368	     16	   2269	    8dd	arch/powerpc/platforms/pseries/vas-sysfs.o

After:
======
   text	   data	    bss	    dec	    hex	filename
   1981	    272	     16	   2269	    8dd	arch/powerpc/platforms/pseries/vas-sysfs.o

Signed-off-by: Huang Xiaojia <huangxiaojia2@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240826150957.3500237-3-huangxiaojia2@huawei.com

Author: hsiaoh2

arch/powerpc/platforms/pseries/vas-sysfs.c

@@ -162,13 +162,13 @@ static const struct sysfs_ops vas_sysfs_ops = {
 	.store	=	vas_type_store,
 };
 
-static struct kobj_type vas_def_attr_type = {
+static const struct kobj_type vas_def_attr_type = {
 		.release	=	vas_type_release,
 		.sysfs_ops      =       &vas_sysfs_ops,
 		.default_groups	=	vas_def_capab_groups,
 };
 
-static struct kobj_type vas_qos_attr_type = {
+static const struct kobj_type vas_qos_attr_type = {
 		.release	=	vas_type_release,
 		.sysfs_ops	=	&vas_sysfs_ops,
 		.default_groups	=	vas_qos_capab_groups,