fixed the commandline in config file.

real6410 default desgin will change the env while download image. so
there have one issue: when i change the commandline in the configs
file,then when I download the image the commandline I changed is not be
used.

And the default commandline is not correct for for yaffs ramdisk.
add uboot printf commandline
Remove the real6410 download menu not used for my platform.