mtd: sh_flctl: Use different OOB layout

The flctl hardware has changed and a new OOB layout must be adapted for
2KiB page size NAND chips when using hardware ECC.
The related bit fields ECCPOS[0-2] are gone — the bits are marked as
reserved now in the datasheet. As there are no official users of the
hardware ECC so far, they are completely removed.

Signed-off-by: Bastian Hecht <hechtb@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>