ARM: dts: sunxi: Fix sunxi-ahci not working on sun4i

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
sunxi-mci: Implement support for mmc on sun4i

While dealing with the amount of bits in the data buf size register anyways,
also properly use all 16 bits of the data buf size on sun5i / sun7i,
rather then only using 15 bits.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>