net: usb: qmi_wwan: fix memory leak for not ip packets

Free the unused skb when not ip packets arrive.

Fixes: c6adf77 ("net: usb: qmi_wwan: add qmap mux protocol support")
Signed-off-by: Daniele Palmas <dnlplm@gmail.com>
Acked-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/qmi_wwan.c

@@ -201,6 +201,7 @@ static int qmimux_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
  break;
  default:
  /* not ip - do not know what to do */
+ kfree_skb(skbn);
  goto skip;
  }