UBI: Fastmap: Wire up WL accessor functions

Use the new WL accessor functions in fastmap.

Signed-off-by: Richard Weinberger <richard@nod.at>
Git-commit: c5c3f3cf969e45c53345283fce0ba11fae7abd32
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>