mtd: Blackfin NFC: delete useless comment about jffs2

The low level NAND driver doesn't care about filesystems, so punt the
local comment indicating otherwise.

Signed-off-by: Barry Song <barry.song@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>