[gpio,dv] Re-add block-level DV for GPIO IP

[martin-velay]

The PR #350 has been reverted by #370 as it was causing troubles. Then a fix has been made upstream on OpenTitan (lowRISC/opentitan@f15d175).

This PR add again the GPIO block level DV and includes the fix from OpenTitan.

The full regression takes now only 3min instead of multiple hours and results are good enough:

          [   legend    ]: [Q: queued, D: dispatched, P: passed, F: failed, K: killed, T: total]                                                                                
00:00:07  [    build    ]: [Q: 0, D: 0, P: 3, F: 0, K: 0, T: 3] 100%                                                                                                            
00:02:23  [     run     ]: [Q: 0, D: 0, P: 907, F: 113, K: 0, T: 1020] 100%                                                                                                     
00:02:49  [  cov_merge  ]: [Q: 0, D: 0, P: 1, F: 0, K: 0, T: 1] 100%                                                                                                            
00:02:53  [ cov_report  ]: [Q: 0, D: 0, P: 1, F: 0, K: 0, T: 1] 100%