You can possibly change it in the ESC firmware if you have access to that. I have done that using BlHeli suite. The only other way of course is to reverse 2 motor leads.
Or, you can start with DJI motor No 2 as your Pixhawk no 1 and go around.
Just place the PixHawk so that DJI M2 an M3 are forward instead of M1 and M2.
Just my 2c.