4823 don't open-code NSEC2MSEC and MSEC2NSEC

*** 1337,1347 ****
          data.len = 0;
          data.maxlen = (databuf == NULL) ? sizeof (bufd): *datalenp;
  
          for (;;) {
                  if (!infinite)
!                         start = gethrtime() / (NANOSEC / MILLISEC);
  
                  switch (poll(&pfd, 1, msec)) {
                  default:
                          if (pfd.revents & POLLHUP)
                                  return (DL_SYSERR);
--- 1337,1347 ----
          data.len = 0;
          data.maxlen = (databuf == NULL) ? sizeof (bufd): *datalenp;
  
          for (;;) {
                  if (!infinite)
!                         start = NSEC2MSEC(gethrtime());
  
                  switch (poll(&pfd, 1, msec)) {
                  default:
                          if (pfd.revents & POLLHUP)
                                  return (DL_SYSERR);
*** 1453,1463 ****
                                          break;
                          }
                  }
  update_timer:
                  if (!infinite) {
!                         current = gethrtime() / (NANOSEC / MILLISEC);
                          msec -= (current - start);
  
                          if (msec <= 0)
                                  return (DLPI_ETIMEDOUT);
                  }
--- 1453,1463 ----
                                          break;
                          }
                  }
  update_timer:
                  if (!infinite) {
!                         current = NSEC2MSEC(gethrtime());
                          msec -= (current - start);
  
                          if (msec <= 0)
                                  return (DLPI_ETIMEDOUT);
                  }