p54pci: increase ring buffer index counter when skipping

I'm afraid, I forgot to add the following lines to
7262d593 ("p54pci: rx tasklet refactoring").

These changes are necessary to ensure loop termination.
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/p54pci.c

@@ -301,9 +301,11 @@ static void p54p_check_rx_ring(struct ieee80211_hw *dev, u32 *index,
 		len = le16_to_cpu(desc->len);
 		skb = rx_buf[i];
 
-		if (!skb)
+		if (!skb) {
+			i++;
+			i %= ring_limit;
 			continue;
-
+		}
 		skb_put(skb, len);
 
 		if (p54_rx(dev, skb)) {