Synthesis and pinout updates

[sgherbst]

This PR covers a bunch of updates related to synthesis, and also updates the top-level pinout.

• Pinout updates:
  • Added pin clk_cgra. This is a gated version of clk_adc that is enable with the JTAG bit en_cgra_clk (default is that it is disabled)
  • Removed pins freq_lvl_cross and ramp_clock since we didn't get them
• Constraints updates:
  • set_dont_touch_network is removed in many places because we do want the synthesis tool to insert buffers on most internal clocks for this tapeout
  • To go along with this change, all high-speed clocks have max_transition constraints set to values that are appropriate for their frequencies, and all black boxes have drive / loading information.
  • Added timing constraints for JTAG based on typical numbers from JTAG cable data sheets
  • Updated pinout for DragonPHY (there were still some holdovers from ButterPHY)
• Quick timing model (QTM) updates:
  • All black boxes now have a QTM and it is used in place of a Verilog stub to ensure that the information in the QTM is really being used.
  • Loading is now scaled from ADK_DRIVING_CELL to fix an issue with capacitance units and improve portability.
• analog_core QTM
  • Pin names have been updated to match what is expected from DC (use . for interfaces but flatten busses).
  • A constraint of 500 ps setup / 0 ps hold has been added for PI control signals
  • ADC outputs are currently all delayed by 1/4 period from the rising edge of clk_adc (exploring more complex possibilities but wanted to submit this PR first)
  • QTMs seem to only allow timing properties based on clock inputs, so ext_clk is considered a fake 1 GHz input for the purpose of the QTM. In the QTM, clk_adc has no relation to ext_clk, but the constraints use create_clock to define identical clocks for ext_clk and clk_adc (except the max_transition for ext_clk is much shorter because it is really an 8 GHz clock)

[codecov-commenter]

Codecov Report

Merging #97 into master will decrease coverage by 0.04%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #97      +/-   ##
==========================================
- Coverage   22.26%   22.22%   -0.05%     
==========================================
  Files          33       33              
  Lines        1909     1908       -1     
==========================================
- Hits          425      424       -1     
  Misses       1484     1484              

Impacted Files	Coverage Δ
dragonphy/views.py	82.78% <100.00%> (-0.14%)	:arrow_down:

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