brcmfmac: fix skb leak in brcmf_sdio_txpkt_prep_sg error path.

Commit 1eb43018 (brcmfmac: fix txglomming scatter-gather packet transfers)
added an allocation of an skb via brcmu_pkt_buf_get_skb() but forgot to
free it on one of the error paths.
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Dave Jones<davej@fedoraproject.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c

@@ -1948,8 +1948,10 @@ static int brcmf_sdio_txpkt_prep_sg(struct brcmf_sdio *bus,
 		if (pkt_pad == NULL)
 			return -ENOMEM;
 		ret = brcmf_sdio_txpkt_hdalign(bus, pkt_pad);
-		if (unlikely(ret < 0))
+		if (unlikely(ret < 0)) {
+			kfree_skb(pkt_pad);
 			return ret;
+		}
 		memcpy(pkt_pad->data,
 		       pkt->data + pkt->len - tail_chop,
 		       tail_chop);