AP_HAL_SMACCM: Send servo outputs to correct ardrone motors.

- Also call "ardrone_motor_init" yet another time during startup.
  It seems to reliably initialize all 4 motors this way, but we
  need a better solution.
AP_HAL_SMACCM: Switch uartA to UART5 on the STM32.

- Change baud rate to 57600.
- This corresponds to the connector on the front of the PX4IOAR,
  which we are using to get wireless serial communication.