RFC: AHCI: libahci is missing DMA

The Allwinner sunxi platforms have patched in the following to enable
DMA. This patch enables DMA controllers for the SUNXI Architecture.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
ARM: sunxi: Add an ahci-platform compatible AHCI driver for the
Allwinner SUNXi series of SoCs

This patch adds support for the sunxi series of SoC's by allwinner. It
plugs into the ahci-platform framework.

Note: Currently it uses a somewhat hackish approach that probably needs
a lot more work, but does the same as the IMX SoC's.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
ARM: sunxi: dts: Add ahci support to a few A10 and A20 boards

This patch adds sunxi sata support to A10 and A20 boards that have such
a connector. Some boards also feature a regulator via a GPIO and support
for this is also added.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>