qcacmn: set mpdu next to null during msdu stitching

In monitor mode, when we try to stitch msdus together into an ampdu
to be sent to the stack (dp_rx_mon_restitch_mpdu_from_msdus),
we aggregate them together via frag_list. In the current code,
for the first msdu in which the frag_list is populated (if there are
more than one msdus to be sent to stack), the next pointer (skb->next)
is not set to NULL. This causes the HDD code to process the next
pointer leading to issues double free issues.

Set the next pointer for the first msdu(with frag_list) to NULL.

Change-Id: I60d1d463c7bbb602e4b199fbb691340ad6247bc5
CRs-Fixed: 2173405

dp/wifi3.0/dp_rx_mon_dest.c

@@ -416,6 +416,7 @@ qdf_nbuf_t dp_rx_mon_restitch_mpdu_from_msdus(struct dp_soc *soc,
 			frag_list_sum_len -= HAL_RX_FCS_LEN;
 			qdf_nbuf_append_ext_list(mpdu_buf, head_frag_list,
 				frag_list_sum_len);
+			qdf_nbuf_set_next(mpdu_buf, NULL);
 		}
 
 		goto mpdu_stitch_done;