sunxi: initialize DRAM after AXP

The default dcdc3 voltage is only 1.2V after reset on the Cubietruck.
This might be too low for correct DRAM controller operation at high
clock frequencies and even the initialization itself may theoretically
fail. So we initialize AXP first. And only then move on to the DRAM
setup.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>