rgbled: try expansion bus first, unless specific bus given
rgbled: try expansion bus first, unless specific bus given

this will allow "rgbled start" to detect which bus the LED is on,
supporting boards with either external or internal LEDs

krbeverx/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,darknight-007/Firmware,PX4/Firmware,jlecoeur/Firmware,darknight-007/Firmware,dagar/Firmware,mcgill-robotics/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,darknight-007/Firmware,mje-nz/PX4-Firmware,jlecoeur/Firmware,mje-nz/PX4-Firmware,darknight-007/Firmware,dagar/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,acfloria/Firmware,acfloria/Firmware,jlecoeur/Firmware,PX4/Firmware,PX4/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,acfloria/Firmware,Aerotenna/Firmware,jlecoeur/Firmware,PX4/Firmware,jlecoeur/Firmware,darknight-007/Firmware,Aerotenna/Firmware,PX4/Firmware,acfloria/Firmware,dagar/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,Aerotenna/Firmware,PX4/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,acfloria/Firmware,dagar/Firmware,krbeverx/Firmware,jlecoeur/Firmware,mcgill-robotics/Firmware,krbeverx/Firmware,mcgill-robotics/Firmware,mcgill-robotics/Firmware,mcgill-robotics/Firmware,dagar/Firmware,krbeverx/Firmware,krbeverx/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware