mtd: cfi_cmdset_0002: code cleanups

- remove disabled code (hasn't been touched since the beginning of git
  and should be reimplemented if really needed)
- convert remaining c++-comments to plain c-style

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Guillaume LECERF <glecerf@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>