mtd: sh_flctl: Simplify the hardware ecc page read/write

As the equation mtd->writesize == eccsteps * eccsize holds, we can
simplify the code. The second loop of the 1st hunk is never entered,
so we delete it.

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>