Build full configuration for zynq including pinout

[kowalik-lukasz]

Platform defining:
Take LiteX -> Read run instruction -> build ready-design for Arty board (using arty.py) -> try to build it on Zynq -> copy Arty definition and arrange it for our board* (don't forget about UART definition!)

Define parts in Platform() class + Remove self.toolchain + comment SDRAM and Ethernet

• Mars ZX2-20-21-* - last from 4 in Enclustra docs

Links:
https://github.com/antmicro/zynq-video-board/blob/master/Documentation/Zynq-Video-Board-v1.2-Pinouts.pdf
https://download.enclustra.com/

[kgugala]

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