mavlink: replace sensor_combined with selected vehicle_imu
mavlink: replace sensor_combined with selected vehicle_imu

 - check all ORB_MULTI_MAX_INSTANCES possible instances for future expansion

krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,PX4/Firmware,acfloria/Firmware,PX4/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,PX4/Firmware,PX4/Firmware,PX4/Firmware,krbeverx/Firmware,krbeverx/Firmware,PX4/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,PX4/Firmware