sunxi: Bananapro: Set LDO4 to 2.5V

According to the Bananapro schematic VDD25-SATA either comes from a
dedicated WL2003E25-5 LTO, or it is connected to LDO4 via a
0 Ohm resistor.

In practice it seems that LDO4 is used, so enable it and set it to 2.5V.

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