UBI has 2 RB-trees to implement PEB protection, which is too
much for simply prevent PEB from being moved for some time.
This patch implements this using lists. The benefits:
1. No need to allocate protection entry on each PEB get.
2. No need to maintain balanced trees and walk them.
Signed-off-by: Xiaochuan-Xu <xiaochuan-xu@cqu.edu.cn>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
7b6c32daec