Divider integration cleanup

Created by: Silabs-ArjanB

Only SEC clean after fixing https://github.com/openhwgroup/cv32e40x/issues/157 first.

Code would have been SEC clean if the original code contained the following in id_stage:

      if (div_en || alu_en) begin // todo: alu_en is needed because CLZ/CTZ depend on div_operator; consider making DIV/REM completely separate
        id_ex_pipe_o.div_operator         <= div_operator;
      end

Area decreases slightly in default configuration with latest synthesizer (vs latest synthesizer)

Signed-off-by: Arjan Bink Arjan.Bink@silabs.com