It seems that we have developed a bad-block-marking "feature" out of
pure laziness:

  "We write two bytes per location, so we dont have to mess with 16 bit
  access."

It's relatively simple to write a 1 byte at a time on x8 devices and 2
bytes at a time on x16 devices, so let's do it.
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>