rtlwifi: fix memory leak for USB device

commit 17bc5586 upstream.

Free skb for received frames with a wrong checksum. This can happen
pretty rapidly, exhausting all memory.

This fixes a memleak (detected with kmemleak). Originally found while
using monitor mode, but it also appears during managed mode (once the
link is up).
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
ACKed-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/wireless/rtlwifi/usb.c

@@ -500,6 +500,8 @@ static void _rtl_usb_rx_process_noagg(struct ieee80211_hw *hw,
 		} else {
 			dev_kfree_skb_any(skb);
 		}
+	} else {
+		dev_kfree_skb_any(skb);
 	}
 }