befs: constify stuff a bit

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
index cc0e082..f168bc8f 100644
--- a/fs/befs/linuxvfs.c
+++ b/fs/befs/linuxvfs.c
@@ -157,7 +157,7 @@
 {
 	struct inode *inode = NULL;
 	struct super_block *sb = dir->i_sb;
-	befs_data_stream *ds = &BEFS_I(dir)->i_data.ds;
+	const befs_data_stream *ds = &BEFS_I(dir)->i_data.ds;
 	befs_off_t offset;
 	int ret;
 	int utfnamelen;
@@ -207,7 +207,7 @@
 {
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;
-	befs_data_stream *ds = &BEFS_I(inode)->i_data.ds;
+	const befs_data_stream *ds = &BEFS_I(inode)->i_data.ds;
 	befs_off_t value;
 	int result;
 	size_t keysize;