NFC: port100: Fix device leak

port100_probe() calls usb_get_dev(), but there is no usb_put_dev()
in port100_disconnect(). The patch adds one.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/nfc/port100.c b/drivers/nfc/port100.c
index 8a0571e..a8555f8 100644
--- a/drivers/nfc/port100.c
+++ b/drivers/nfc/port100.c
@@ -1509,6 +1509,7 @@
 
 	usb_free_urb(dev->in_urb);
 	usb_free_urb(dev->out_urb);
+	usb_put_dev(dev->udev);
 
 	kfree(dev->cmd);