[Spidriver] Minor enhancements

src/shared/drivers/Xbee/Xbee.h

src/shared/drivers/spi/SPIBus.cpp

src/shared/drivers/spi/SPIInterface.h

src/shared/sensors/L3GD20.h

src/shared/sensors/MS580301BA07/MS580301BA07.h

src/tests/catch/spidriver/FakeSPIBus.h

src/tests/catch/spidriver/test-spidriver.cpp

src/tests/drivers/test-l3gd20.cpp