sunxi: add basic V3s support

Basic U-Boot support is now present for V3s.

Some memory addresses are changed specially for V3s, as the original
address map cannot fit into a so small DRAM.

As the DRAM controller code needs a big refactor, the SPL support is
disabled in this version.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>