ARM: palmtreo: add docg4 device initialization

This patch adds initialization of the docg4 nand flash device to the treo680.

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Acked-by: Tomas Cech <sleep_walker@suse.cz>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>