ARM: sunxi: Add clock and uart to sunxi headers

This patch aims to add header files for the suniv.
The header files included add support for uart, and clocks.

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