nfc: pn533: Fix double free when pn533_fill_fragment_skbs() fails

skb is already freed by dev_kfree_skb in pn533_fill_fragment_skbs,
but follow error handler branch when pn533_fill_fragment_skbs()
fails, skb is freed again, results in double free issue. Fix this
by not free skb in error path of pn533_fill_fragment_skbs.

Fixes: 963a82e0 ("NFC: pn533: Split large Tx frames in chunks")
Fixes: 93ad4202 ("NFC: pn533: Target mode Tx fragmentation support")
Signed-off-by: Chengfeng Ye <cyeaa@connect.ust.hk>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/nfc/pn533/pn533.c

@@ -2216,7 +2216,7 @@ static int pn533_fill_fragment_skbs(struct pn533 *dev, struct sk_buff *skb)
 		frag = pn533_alloc_skb(dev, frag_size);
 		if (!frag) {
 			skb_queue_purge(&dev->fragment_skb);
-			break;
+			return -ENOMEM;
 		}
 
 		if (!dev->tgt_mode) {
@@ -2285,7 +2285,7 @@ static int pn533_transceive(struct nfc_dev *nfc_dev,
 		/* jumbo frame ? */
 		if (skb->len > PN533_CMD_DATAEXCH_DATA_MAXLEN) {
 			rc = pn533_fill_fragment_skbs(dev, skb);
-			if (rc <= 0)
+			if (rc < 0)
 				goto error;
 
 			skb = skb_dequeue(&dev->fragment_skb);
@@ -2353,7 +2353,7 @@ static int pn533_tm_send(struct nfc_dev *nfc_dev, struct sk_buff *skb)
 	/* let's split in multiple chunks if size's too big */
 	if (skb->len > PN533_CMD_DATAEXCH_DATA_MAXLEN) {
 		rc = pn533_fill_fragment_skbs(dev, skb);
-		if (rc <= 0)
+		if (rc < 0)
 			goto error;
 
 		/* get the first skb */