UBI: Fastmap: Do not add vol if it already exists
UBI: Fastmap: Do not add vol if it already exists

During fastmap attaching, check if a volume already exists when adding
the volume to volume tree. NOTE that the issue cannot happen, only if
the on-flash fastmap data is modified.

Signed-off-by: Sheng Yong <ce77ec10379c6f281208b7b41f03fd701be51d81@huawei.com>
Signed-off-by: Richard Weinberger <320bca71fc381a4a025636043ca86e734e31cf8b@nod.at>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs