ARM: sunxi: Introduce Allwinner A80 support

The Allwinner A80 is a new Cortex octo-core A7/A15 big.LITTLE SoC.
While it's processor cores and interconnecting bus are new, it
re-uses many peripherals found in earlier Allwinner SoCs.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Tested-by: Andreas Färber <afaerber@suse.de>