ARM: sunxi: Introduce Allwinner H3 support

The Allwinner H3 is a quad-core Cortex-A7-based SoC. It is very similar
to other sun8i family SoCs like the A23.

Signed-off-by: Jens Kuske <jenskuske@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>