Fix circuit so power is constant, instead of controlled by wall switch?
From the junction box where the power runs into garage....   you say you have one wire that runs to switch?  so hot or switch leg is on either white or black wire on that "wire" that runs to switch?  

You simply need to open junction box and identify wire that has power incoming to garage, wire that goes to lights, and wire that goes to garage door openor...  From the hot wire...  connect white and blacks to outlet that garage door is hooked up to.  Then if you have a white or black being used as either power or switch leg to the lights from the switch....   identify which is constant hot and which is switched... either white or black and splice the the non constant hot (switch leg) to the light hot in the junction box.

Or provide more details....