dm: core: Add option to configure an offset for the address translation

Some platforms need to ability to configure an offset to the standard
addresses extracted from the device-tree. This patch allows this by
adding a function to DM to configure this offset (if needed).

Signed-off-by: Stefan Roese <sr@denx.de>
Acked-by: Simon Glass <sjg@chromium.org>
Cc: Simon Glass <sjg@chromium.org>
Fixed space before tab:
Signed-off-by: Simon Glass <sjg@chromium.org>