Add baudrate setting in HAL SPI.
Use default SPI configuration in arduino frontend.
Add SPI support for TI board :
 - SPI has been tested with RF24 example and seems to work;
 - Callbacks are not implemented;
 - Only SSI0 has been tested.
Change GPIO pin on RF24 example to match lm4f120xl board.
Fix regression of gpio configuration in STM32 SPI HAL