ocfs2/trivial: Remove unused variable in ocfs2_rename.

With indexed dir enabled, now we use ocfs2_dir_lookup_result to
wrap all the bh used for dir. So remove the 2 unused variables.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>