add working DDR3 xilinx sp605

[vanbwodonk]

Hi, i have old board Xilinx-SP605 but litex don't have example target for this board.
add target with working DDR3 and DVI phy (CH7301),
but i need to patch litedram too:

# PHY settings -----------------------------------------------------------------------------
        self.settings = PhySettings(
            phytype       = "S6QuarterRateDDRPHY",
            memtype       = "DDR3",
            databits      = databits,
            dfi_databits  = 2*databits,
            nranks        = nranks,
            nphases       = nphases,
            rdphase       = 0,
            wrphase       = 1,
            # rdcmdphase    = 1,
            # wrcmdphase    = 0,
            cl            = 5,
            cwl           = 6,
            read_latency  = 6//2+1,
            write_latency = 2//2
        )

i need to disable rdcmdphase & wrcmdphase.

[vanbwodonk]

SS bios boot with DDR3: