Fianlly managed to boot nitdroid using the u-boot+k48.bin. Nitdroid uImage is on the sdcard without using multiboot. It directly loods the kernel from ths SDcard . But I still use the maemo rootfs as a initial ramdisk and created a special script to setup the system and switch the rootfs to the sdcard.

I went tot hte u-boot console prompt. Gave the command "setenv atagaddr ${init_atagaddr}" follwoed by run emmcboot.

In the end I;d like to have an initfs on the sdcard so I can boor without using the meamo rootfs.