[syn/cdc] Tune SDC file to fix all SDC warnings/errors in CDC
[syn/cdc] Tune SDC file to fix all SDC warnings/errors in CDC

This introduces some more flexibility to the SDC file so that we can
reuse it for open-source-only CDC runs where the hookup paths have
different hierarchical names.

Also, there are a few constraints that CDC does not understand, and we
introduce a variable to exclude them conditionally for CDC flows.

Signed-off-by: Michael Schaffner <a005a2d3342a687ea2d05360c953107acbe83e08@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan