Setting DC-bias on LVDS receiver with internal 100ohm differential termination
If you disable the internal termination, you could externally terminate to 1.2V / 50 ohms on each input.  However, with internal 100 ohm termination enabled, you should use much higher value resistors to set the common mode voltage as shown below from this Maxim app note.  The larger resistors set the common mode voltage, but do not interfere with the termination.

Your signal integrity should be a little better with internal termination, so the higher value external resistors are probably the best solution.