擦除nand flash + [nand flash command]

    "nand - NAND sub-systemn",
    "info - show available NAND devicesn"
    "nand device [dev] - show or set current devicen"
    "nand read[.jffs2] - addr off|partition sizen"
    "nand write[.jffs2] - addr off|partiton size - read/write `size' bytes startingn"
    " at offset `off' to/from memory address `addr'n"
    "nand erase [clean] [off size] - erase `size' bytes fromn"
    " offset `off' (entire device if not specified)n"
    "nand bad - show bad blocksn"
    "nand dump[.oob] off - dump pagen"
    "nand scrub - really clean NAND erasing bad blocks (UNSAFE)n"
    "nand markbad off - mark bad block at offset (UNSAFE)n"
    "nand biterr off - make a bit error at offset (UNSAFE)n"
    "nand lock [tight] [status] - bring nand to lock state or display locked pagesn"
    "nand unlock [offset] [size] - unlock sectionn";