7122 fix negative timestamps with nsec == 0 in nfs4_time_ntov()

*** 493,503 ****
  
          /* Invalid to specify 1 billion (or more) nsecs */
          if (ntime->nseconds >= 1000000000)
                  return (EINVAL);
  
!         if (ntime->seconds < 0) {
                  sec = ntime->seconds + 1;
                  nsec = -1000000000 + ntime->nseconds;
          } else {
                  sec = ntime->seconds;
                  nsec = ntime->nseconds;
--- 493,503 ----
  
          /* Invalid to specify 1 billion (or more) nsecs */
          if (ntime->nseconds >= 1000000000)
                  return (EINVAL);
  
!         if (ntime->seconds < 0 && ntime->nseconds != 0) {
                  sec = ntime->seconds + 1;
                  nsec = -1000000000 + ntime->nseconds;
          } else {
                  sec = ntime->seconds;
                  nsec = ntime->nseconds;