mach-sunxi: Add support for SUNIV architecture

Add support for the suniv architecture, which is newer ARM9 SoCs by
Allwinner. The design of it seems to be a mixture of sun3i, sun4i and
sun6i.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>