This converts the following to Kconfig:
   CONFIG_JFFS2_DEV
   CONFIG_JFFS2_LZO
   CONFIG_JFFS2_NAND
   CONFIG_JFFS2_PART_OFFSET
   CONFIG_JFFS2_PART_SIZE
Signed-off-by: NTom Rini <trini@konsulko.com>