HOTFIX: correct some logic errors with SPI chipselect generation.

Tested by Tridge.

apps/drivers/boards/px4fmu/px4fmu_spi.c

@@ -92,21 +92,21 @@ __EXPORT void stm32_spi1select(FAR struct spi_dev_s *dev, enum spi_dev_e devid,
 	case PX4_SPIDEV_GYRO:
 		/* Making sure the other peripherals are not selected */
 		stm32_gpiowrite(GPIO_SPI_CS_GYRO, !selected);
-		stm32_gpiowrite(GPIO_SPI_CS_MPU, selected);
-		stm32_gpiowrite(GPIO_SPI_CS_ACCEL, selected);
+		stm32_gpiowrite(GPIO_SPI_CS_MPU, 1);
+		stm32_gpiowrite(GPIO_SPI_CS_ACCEL, 1);
 		break;
 
 	case PX4_SPIDEV_ACCEL:
 		/* Making sure the other peripherals are not selected */
 		stm32_gpiowrite(GPIO_SPI_CS_ACCEL, !selected);
-		stm32_gpiowrite(GPIO_SPI_CS_MPU, selected);
-		stm32_gpiowrite(GPIO_SPI_CS_GYRO, selected);
+		stm32_gpiowrite(GPIO_SPI_CS_MPU, 1);
+		stm32_gpiowrite(GPIO_SPI_CS_GYRO, 1);
 		break;
 
 	case PX4_SPIDEV_MPU:
 		/* Making sure the other peripherals are not selected */
-		stm32_gpiowrite(GPIO_SPI_CS_ACCEL, selected);
-		stm32_gpiowrite(GPIO_SPI_CS_GYRO, selected);
+		stm32_gpiowrite(GPIO_SPI_CS_ACCEL, 1);
+		stm32_gpiowrite(GPIO_SPI_CS_GYRO, 1);
 		stm32_gpiowrite(GPIO_SPI_CS_MPU, !selected);
 		break;
 
@@ -125,7 +125,7 @@ __EXPORT uint8_t stm32_spi1status(FAR struct spi_dev_s *dev, enum spi_dev_e devi
 __EXPORT void stm32_spi3select(FAR struct spi_dev_s *dev, enum spi_dev_e devid, bool selected)
 {
 	/* there can only be one device on this bus, so always select it */
-	stm32_gpiowrite(GPIO_SPI_CS_SDCARD, 0);
+	stm32_gpiowrite(GPIO_SPI_CS_SDCARD, !selected);
 }
 
 __EXPORT uint8_t stm32_spi3status(FAR struct spi_dev_s *dev, enum spi_dev_e devid)