Revert "mtd: ubi: Read disturb infrastructure"

This reverts commit 732b65bc.

This patch is part of the "read-disturb implementation" set of patches. It
was decided to take different approach in addressing the read disturb,
thus the whole patch series is reverted in order to simplify the code and
reduce memory footprint.

Conflicts and compilation errors were addressed.

Change-Id: I754c772cb07aa571f31b641c461b26fea90d5e78
Signed-off-by: Tanya Brokhman <tlinder@codeaurora.org>