DRAM chip varies, and one code cannot satisfy all DRAMs.
Add options to select a timing set.
Currently only DDR3-1333 (the original set) is added into it.
Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>
