Btrfs: constify dentry_operations

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d3585cb..d960492 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5840,6 +5840,6 @@
 	.removexattr	= btrfs_removexattr,
 };
 
-struct dentry_operations btrfs_dentry_operations = {
+const struct dentry_operations btrfs_dentry_operations = {
 	.d_delete	= btrfs_dentry_delete,
 };