sunxi: Replace the pcDuino3 config with FDT version

We currently have Linksprite_pcDuino3 and Linksprite_pcDuino3_fdt. Drop the
former in favour of the latter.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>