samples: configfs: Constify struct configfs_item_operations and configfs_group_operations

'struct configfs_item_operations' and 'configfs_group_operations' are not
modified in this driver.

Constifying these structures moves some data to a read-only section, so
increases overall security, especially when the structure holds some
function pointers.

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
   7507	   6504	     64	  14075	   36fb	samples/configfs/configfs_sample.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
   7827	   6184	     64	  14075	   36fb	samples/configfs/configfs_sample.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/70c5fd68fcc4d3ba1f18002012fae19acf4ce50b.1767007414.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>

Author: tititiou36

samples/configfs/configfs_sample.c

@@ -158,7 +158,7 @@ static void simple_child_release(struct config_item *item)
 	kfree(to_simple_child(item));
 }
 
-static struct configfs_item_operations simple_child_item_ops = {
+static const struct configfs_item_operations simple_child_item_ops = {
 	.release	= simple_child_release,
 };
 
@@ -215,15 +215,15 @@ static void simple_children_release(struct config_item *item)
 	kfree(to_simple_children(item));
 }
 
-static struct configfs_item_operations simple_children_item_ops = {
+static const struct configfs_item_operations simple_children_item_ops = {
 	.release	= simple_children_release,
 };
 
 /*
  * Note that, since no extra work is required on ->drop_item(),
  * no ->drop_item() is provided.
  */
-static struct configfs_group_operations simple_children_group_ops = {
+static const struct configfs_group_operations simple_children_group_ops = {
 	.make_item	= simple_children_make_item,
 };
 
@@ -292,7 +292,7 @@ static struct configfs_attribute *group_children_attrs[] = {
  * Note that, since no extra work is required on ->drop_item(),
  * no ->drop_item() is provided.
  */
-static struct configfs_group_operations group_children_group_ops = {
+static const struct configfs_group_operations group_children_group_ops = {
 	.make_group	= group_children_make_group,
 };