Rather than duplicate a defconfig for each difference
between platforms, we can choose to pick a basic defconfig and
manipulate it at run-time using config fragments. Here we're
adding a new fragment to over-ride the RAM start point to 0x0.

Cc: Arnd Bergmann
Signed-off-by: Lee Jones
Acked-by: Arnd Bergmann
Signed-off-by: Maxime Coquelin