sunxi: add LPDDR3 DRAM type support for DesignWare-like DRAM controller

Some A64 boards (SoPine and Pinebook production batch) use LPDDR3 DRAM
chips.

Add support for LPDDR3 DRAM in the DesignWare-like DRAM controller code.

Real LPDDR3 chips' support is not added yet in this commit.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>