iwlwifi: fix-up some merge damage from commit 0d6c4a2e

Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn-rx.c

@@ -764,7 +764,8 @@ static void iwlagn_pass_packet_to_mac80211(struct iwl_priv *priv,
 	fraglen = len - hdrlen;
 
 	if (fraglen) {
-		int offset = (void *)hdr - rxb_addr(rxb) + rxb_offset(rxb);
+		int offset = (void *)hdr + hdrlen -
+			     rxb_addr(rxb) + rxb_offset(rxb);
 
 		skb_add_rx_frag(skb, 0, rxb_steal_page(rxb), offset,
 				fraglen, rxb->truesize);