Retire signal not correct for CSRs

Created by: GTumbush

Opening this issue based on call March 10, 2020.

The tracer does not support printing CSR's to the tracer file. I attempted to compare cv32e40p mstatus_q to mstatus predicted by the Imperas ISS and experienced inconsistent timing of mstatus_q update for the mret and ecall instructions.

The mret instruction updates mstatus_q to 8, 1 clock cycle after the retire signal (see below).

The ecall instruction updates mstatus_q to 6, 2 clock cycles before the retire signal (see below).

The software to produce the above is in the attached zip file. riscv_arithmetic_basic_test_0.zip