sh: ap325rxa: create CPLD data area in mtd

AP320 and AP325RXA has CPLD data in NOR Flash.
If this area erased, this board can not boot.
This patch create CPLD data area and set writeable mask bit.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu.nobuhiro@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>