uio: Constify struct kobj_type

These 'struct kobj_type' are not modified. They are only used in
kobject_init() which takes a 'const struct kobj_type *ktype'
parameter.

Constifying these structure and moving them to a read-only
section (from data to text), and can increase over all security.

```
[Before]
text data bss dec hex filename
10330 1908 20 12258 2fe2 drivers/uio/uio.o

[After]
text data bss dec hex filename
10458 1844 20 12322 3022 drivers/uio/uio.o
```

Signed-off-by: Hongbo Li <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/uio/uio.c

···
 	.show = map_type_show,
 };
 
-static struct kobj_type map_attr_type = {
+static const struct kobj_type map_attr_type = {
 	.release	= map_release,
 	.sysfs_ops	= &map_sysfs_ops,
 	.default_groups	= map_groups,
···
 	.show = portio_type_show,
 };
 
-static struct kobj_type portio_attr_type = {
+static const struct kobj_type portio_attr_type = {
 	.release	= portio_release,
 	.sysfs_ops	= &portio_sysfs_ops,
 	.default_groups	= portio_groups,