Nuttx bringup fix headers

This is the clean up that made sense:
Did you run into issues with the px4fmu-v1 build for:

void stm32_spi2select(FAR struct spi_dev_s *dev, enum spi_dev_e devid, bool selected);
uint8_t stm32_spi2status(FAR struct spi_dev_s *dev, enum spi_dev_e devid);

As missing prototypes?