ARM: kwimage: fix v0 format

This patch fix the kwimage tools for version 0 fileformat used for kirkwood
Tested on sheevaplug

Signed-off-by: Gerald Kerma <drEagle@doukki.net>
Tested-by: Stefan Roese <sr@denx.de>
Reviewed-by: Stefan Roese <sr@denx.de>
Acked-By: Prafulla Wadaskar <prafulla@marvell.com>