mm/huge_memory.c: 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.

Link: http://lkml.kernel.org/r/1501157240-3876-1-git-send-email-arvind.yadav.cs@gmail.comSigned-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/huge_memory.c

@@ -328,7 +328,7 @@ static struct attribute *hugepage_attr[] = {
 	NULL,
 };
 
-static struct attribute_group hugepage_attr_group = {
+static const struct attribute_group hugepage_attr_group = {
 	.attrs = hugepage_attr,
 };