mtd: add fixup for S29NS512P NOR flash.

Spansion S29NS512P flash uses a 16bit transfer to report number
of sectors instead of two 8bit accesses as CFI specifies.

Artem: remove warning message which said that we are applying the
fixup - no need to scary the user unnecessarily.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>