NXFFS: more NAND-Releated changes; don't fail if a block read fails.  That might just be a NAND uncorrectable bit error.  Make scanning of the device on startup optional.  This might have introduced some NXFFS issure -- To be determined

NXFFS: When dumping the MTD content, don't abort on a read error.  For NAND, the read error probably just means that an uncorrectable ECC was encountered

NXFFS: First of many changes for NAND.  NAND reports read errors on ECC failures.  NXFFS can't just give up in these cases and must treat read failures like bad blocks