const: mark remaining address_space_operations const

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
index c668bca..6a2711f 100644
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -46,7 +46,7 @@
 	INIT_LIST_HEAD(&btnc->i_mmap_nonlinear);
 }
 
-static struct address_space_operations def_btnode_aops = {
+static const struct address_space_operations def_btnode_aops = {
 	.sync_page		= block_sync_page,
 };