sunxi: make V3s DRAM initialization more proper

Previously, because we have no source code about the DRAM initialization
of V3s and missing some configurations (delays and MBUS QoS info), our
V3s DRAM initialization sequence is hacked from the H3 one.

As the SDK shipped with PineCube contains source code for V3s libdram,
we can retrieve these information from it and tweak some other magic
bits.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Jagan Teki <jagan@amarulasolutions.com>