PX4: allow flight mode setup without sensors

Before this change it is not allowed to set up the flight modes unless
all sensor calibrations are completed.

I don't think that makes sense because it is possible to calibrate RC
without having the sensors calibrated, and it's the logical next step
right after that.

It is also a problem if HITL (hardware-in-the-loop) is used where the
sensors are not marked as calibrated but you still need to be able to
configure the flight modes. This is what prompted me to suggest this
change.

src/AutoPilotPlugins/PX4/PX4AutoPilotPlugin.cc

@@ -156,8 +156,6 @@ QString PX4AutoPilotPlugin::prerequisiteSetup(VehicleComponent* component) const
                 return _airframeComponent->name();
             } else if (_radioComponent && !_radioComponent->setupComplete()) {
                 return _radioComponent->name();
-            } else if (_sensorsComponent && !_sensorsComponent->setupComplete()) {
-                return _sensorsComponent->name();
             }
         }
     } else if (qobject_cast<const PX4RadioComponent*>(component)) {