sensors: mag reload calibration parameters when first seen (#12586)

* fixes UAVCAN MAG calibration application after reboot

src/modules/sensors/voted_sensors_update.cpp

@@ -764,6 +764,9 @@ void VotedSensorsUpdate::mag_poll(vehicle_magnetometer_s &magnetometer)
 				int32_t priority = 0;
 				orb_priority(_mag.subscription[uorb_index], &priority);
 				_mag.priority[uorb_index] = (uint8_t)priority;
+
+				/* force a scale and offset update the first time we get data */
+				parameters_update();
 			}
 
 			matrix::Vector3f vect(mag_report.x, mag_report.y, mag_report.z);