sunxi: switch Allwinner A10s/A13 boards to OF_UPSTREAM

sunxi: switch Allwinner A10s/A13 boards to OF_UPSTREAM

In contrast to some other Allwinner SoCs, there is no difference between
the DTs for the Allwinner A10s/A13 SoCs (sun5i) between the U-Boot and the
Linux kernel repository.

Remove the old copies of the A10s/A13 related .dts and .dtsi files, and
switch most of sun5i boards over to use OF_UPSTREAM.

There are two boards for which we don't have DTs in the kernel tree.
Keep those two .dts files in the legacy U-Boot DT directory, and let
their defconfig opt out of OF_UPSTREAM.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Sumit Garg <sumit.garg@linaro.org>