wireless: iwlegacy: Constify attribute_group structures.

attribute_group are not supposed to change at runtime. All functions
working with attribute_group provided by <linux/sysfs.h> work
with const attribute_group. So mark the non-const structs as const.
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/wireless/intel/iwlegacy/4965-mac.c

@@ -4654,7 +4654,7 @@ static struct attribute *il_sysfs_entries[] = {
 	NULL
 };
 
-static struct attribute_group il_attribute_group = {
+static const struct attribute_group il_attribute_group = {
 	.name = NULL,		/* put in device directory */
 	.attrs = il_sysfs_entries,
 };