freenect: initialize the 'transferred' variable used in bulk transfers

This is in order to make the printouts in the error path of the callers
of fnusb_bulk() show a saner value when libusb does not touch the
variable (i.e. when a transfer fails).

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>

Author: Antonio Ospite

src/usb_libusb10.c

@@ -575,6 +575,7 @@ FN_INTERNAL int fnusb_control(fnusb_dev *dev, uint8_t bmRequestType, uint8_t bRe
 
 #ifdef BUILD_AUDIO
 FN_INTERNAL int fnusb_bulk(fnusb_dev *dev, uint8_t endpoint, uint8_t *data, int len, int *transferred) {
+	*transferred = 0;
 	return libusb_bulk_transfer(dev->dev, endpoint, data, len, transferred, 0);
 }