ARM: sunxi: add support for H2+ SoC

Allwinner H2+ is a quad-core Cortex-A7 SoC.

It is very like H3, that they share the same SoC ID (0x1680), and H3
memory maps as well as drivers works well on the SoC.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>