Updating liteEth to latest legacy commit fails due to FlipFlop removal

[mithro]

FlipFlop seems to have been removed from liteEth in enjoy-digital/liteeth@2b6dfa6

- make firmware (atlys hdmi2eth) (prerun)
---------------------------------------------
cd third_party/misoc && python3 make.py -X ../.. -t atlys_hdmi2eth -Ot firmware_filename ../../firmware/lm32/firmware.bin -Op programmer openocd -Ob ise_path /home/travis/build/timvideos/HDMI2USB-misoc-firmware/build/Xilinx/opt/Xilinx/ build-headers
Traceback (most recent call last):
  File "make.py", line 91, in <module>
    soc = top_class(platform, **top_kwargs)
  File "../../targets/atlys_hdmi2eth.py", line 120, in __init__
    self.submodules.encoder_streamer = UDPStreamer(convert_ip("192.168.1.15"), 8000)
  File "/home/travis/build/timvideos/HDMI2USB-misoc-firmware/gateware/streamer/__init__.py", line 21, in __init__
    self.submodules.level = level = FlipFlop(max=fifo_depth+1)
NameError: name 'FlipFlop' is not defined
make: *** [firmware-lm32] Error 1

[enjoy-digital]

403c33e should fix that.

[mithro]

This has been fixed. I've updated the submodules to the latest legacy versions in #138