CIFS: Fix duplicate line introduced by clone_file_range patch

Commit 04b38d60 ("vfs: pull btrfs clone API to vfs layer")
added a duplicated line (in cifsfs.c) which causes a sparse compile
warning.

Signed-off-by: Steve French <steve.french@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>