UBI: Call scan_all() with correct offset in error case

If we find an invalid fastmap we have to scan from the very beginning.
Otherwise we leak the first 64 PEBs.

Change-Id: I7ded8ab07de9b21478bc284e7c2b655f9aa7707f
Reported-and-tested-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Git-commit: 4b3e0a25aa5518892ec8dbfafdd6a57789aa0c22
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>