ocfs2: Fix oops in ocfs2_fast_symlink_readpage() code path

Commit ea022dfb was missing a var init.

Reported-and-Tested-by: Vincent Etienne <vetienne@aprogsys.com>
Signed-off-by: Sunil Mushran <sunil.mushran@gmail.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>