sunxi: switch Allwinner A80 boards to OF_UPSTREAM

sunxi: switch Allwinner A80 boards to OF_UPSTREAM

In contrast to some other Allwinner SoCs, there is no difference between
the DTs for the Allwinner A80 SoCs (sun9i) between the U-Boot and the
Linux kernel repository.

Remove the old copies of the A80 related .dts and .dtsi files, and switch
most of sun9i boards over to use OF_UPSTREAM.

There is the Sunchip CX-A99 (family of) board(s) for which we don't have
a DT in the kernel tree. Keep the .dts file in the legacy U-Boot DT
directory, and let the board's defconfig opt out of OF_UPSTREAM.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>