add new board files for VC707 and VCU118

add new board files for VC707 and VCU118, only specified limited ports for VCU118, including clock, reset and DDR4

platforms/colorlight_5a_75b.py: fix sdram_clock and sdram a pins

Changed wrong imports for fomu board.

targets/EthernetSoC: be sure memory region is added before adding Wishbone Slave (required by new SoC)

We initially wanted to provide different level of support for the platforms/targets, mainly
to avoid too much maintenance and let each contributor update its contributed platforms and
targets, but it's easier to update all platforms/targets all-together when LiteX evolves or
changes (and that's what has been done on litex-boards since the creation of the repository).
So let just simplify things and avoid this differentiation.

Things weren't quite right for adding a CPU.  This fixes that by
correcting the placer arguments, memory map, and USB type.

Signed-off-by: Sean Cross <sean@xobs.io>

de10nano: cleanup a bit, rename SDRAMSoC to MiSTerSDRAMSoC and argument to --with-mister-sdram to make it clear that it's using the MiSTer SDRAM extension board.

Add de10 nano board

add iostandard to hdmi

Tested with:
./colorlight_5a_75b.py --cpu-type=picorv32 --uart-name=crossover --with-etherbone --csr-csv=csr.csv

Load with following script:
#!/usr/bin/env python3

# Load ---------------------------------------------------------------------------------------------

def load():
    import os
    f = open("openocd.cfg", "w")
    f.write(
"""
interface ftdi
ftdi_vid_pid 0x0403 0x6011
ftdi_channel 0
ftdi_layout_init 0x0098 0x008b
reset_config none
adapter_khz 25000
jtag newtap ecp5 tap -irlen 8 -expected-id 0x41111043
""")
    f.close()
    os.system("openocd -f openocd.cfg -c \"transport select jtag; init; svf soc_etherbonesoc_colorlight_5a_75b/gateware/top.svf; exit\"")
    exit()

if __name__ == "__main__":
    load()


Then start lxserver:
lxserver --udp

And run following script:

#!/usr/bin/env python3

import sys

from litex import RemoteClient

wb = RemoteClient()
wb.open()

# # #

while True:
    if wb.regs.uart_xover_rxempty.read() == 0:
        print(chr(wb.regs.uart_xover_rxtx.read()), end="")
        sys.stdout.flush()

# # #

wb.close()