sunxi: A523: add DDR3 DRAM support

sunxi: A523: add DDR3 DRAM support

Add reverse engineered code to add support for DDR3 DRAM chips on the
Allwinner A523 DRAM controller.
The timings are copying what boot0 set up on the X96QPro+ TV box, though
they seem quite suboptimal, with longer latencies that would be required
for DDR3-1600. The chips are also actually capable of DDR3-1833, so
there is room for future improvement.

Signed-off-by: Mikhail Kalashnikov <iuncuim@gmail.com>
[Andre: rework to copy from H616 DDR3 driver, calculate timings]
Signed-off-by: Andre Przywara <andre.przywara@arm.com>