[][OpenWrt Dev][Add empty page bitflips detection and fix for mtk-snand driver]

Add support for mtk-snand driver to detect and fix bitflips of empty pages

Also, change to ecc strength of mtd layer to ecc strength of a sector,
and report max bitflips of sectors within a page.


Change-Id: I0cb71808076ab809bdbbe98b59859394c79c59f9
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4520684
4 files changed