[][OpenWrt Dev][nmbm: checking bad block marker should use raw mode]

Change the checking bad block function to use raw read mode

It's necessary to use raw mode to check the bad block marker, otherwise
the marker may be corrected by ECC is ECC stringth is greater than 8.


Change-Id: I4718e13e18a2b33e25a61339db79744ea4545a42
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4649341
1 file changed