GTA04A5 has been produced with MCP chips either with
 512MB RAM +  512MB NAND
 512MB RAM + 1024MB NAND
1024MB RAM +  512MB OneNAND

RAM setup is done by U-Boot (MLO/SPL) but OneNAND needs
a different setup of the GPMC. So we need to derive a
DTB variant that modifies the gpmc and nand setup.
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>