Add RVFI to Ariane

Created by: JeanRochCoulon

The RVFI has been implemented to generate execution trace. This RFVI implementation is synthetizable which is convenient to keep the trace functionility in gate simulation. Only the signals useful to generate instruction execution trace have been implemented. In the near future, our goal is to implement all the signals.

Makefile, rvfi_tracer_pck.sv, ariane.sv, ariane_testharness.sv : - rvfi_tracer.sv: add RVFI tracer and debug support. rvfi_tracer is a module added in ariane-testharness.sv. - RVFI ports are added to ariane module and connected to rvfi_tracer module - RVFI_TRACE enables RVFI trace generation