ARM: sunxi: Add basic A31 support

Add a new sun6i machine that supports UART and MMC.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[wens@csie.org: use SPDX labels, adapt to Kconfig system, drop ifdef
		around mmc and smp code, drop MACH_TYPE]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Ian Campbell <ijc@hellion.org.uk>