px4fmu-v5:Insure the VBUS signal is low if USB is not connected.

Dispite what the ref manaul says. Some HW needs the added pull
   down to insure the pin reads low when not plugged in to USB.

src/drivers/boards/px4fmu-v5/board_config.h

@@ -425,7 +425,7 @@ __BEGIN_DECLS
  *
  * PA9  OTG_FS_VBUS VBUS sensing
  */
-#define GPIO_OTGFS_VBUS         /* PA9 */ (GPIO_INPUT|GPIO_FLOAT|GPIO_SPEED_100MHz|GPIO_PORTA|GPIO_PIN9)
+#define GPIO_OTGFS_VBUS         /* PA9 */ (GPIO_INPUT|GPIO_PULLDOWN|GPIO_SPEED_100MHz|GPIO_PORTA|GPIO_PIN9)
 
 /* High-resolution timer */
 #define HRT_TIMER		     8  /* use timer8 for the HRT */

src/drivers/boards/px4fmu-v5/px4fmu_init.c

@@ -229,10 +229,9 @@ stm32_boardinitialize(void)
 
 	stm32_spiinitialize();
 
-	/* Power on the SD Card */
-
-	SD_CARD_POWER_CTRL(true);
+	/* configure USB interfaces */
 
+	stm32_usbinitialize();
 
 }