UBI: Fastmap: Remove bogus ubi_assert()

It is legal to have PEBs left in the used list.
This can happen if UBI copies a PEB and a powercut happens
between writing a new fastmap and adding this PEB into the EBA table.
In this case the old PEB will be used.

Signed-off-by: Richard Weinberger <richard@nod.at>
Git-commit: a83832a7c8d023f446ec865926190951bd18a4b1
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


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