Splitted out the dts file and create the new dts for the 256 MByte RAM and
the 512 MB RAM version.
Migrate both versions to the common board detection.
The install the 512 MByte Version on a board running the 256 MByte image,
a forceful sysupgrade with the -F flag is required.
Signed-off-by: Davide Ammirata <list@davidea.it>
