ath9k: fix dma mapping leak of rx buffer upon rmmod

We were claiming DMA buffers on the RX tasklet but never
upon a simple module removal.

Cc: stable@kernel.org
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath9k/recv.c

@@ -344,8 +344,13 @@ void ath_rx_cleanup(struct ath_softc *sc)
 
 	list_for_each_entry(bf, &sc->rx.rxbuf, list) {
 		skb = bf->bf_mpdu;
-		if (skb)
+		if (skb) {
+			dma_unmap_single(sc->dev,
+					 bf->bf_buf_addr,
+					 sc->rx.bufsize,
+					 DMA_FROM_DEVICE);
 			dev_kfree_skb(skb);
+		}
 	}
 
 	if (sc->rx.rxdma.dd_desc_len != 0)