qcacmn: Initialize qdf_nbuf_t before use

Initialize qdf_nbuf_t variables before use.

Change-Id: I4922de4c9f31c98dc745802dbb23a0757795769d
CRs-Fixed: 2587451

dp/wifi3.0/dp_rx.c

@@ -1033,7 +1033,7 @@ static inline bool dp_rx_adjust_nbuf_len(qdf_nbuf_t nbuf, uint16_t *mpdu_len)
  */
 qdf_nbuf_t dp_rx_sg_create(qdf_nbuf_t nbuf, uint8_t *rx_tlv_hdr)
 {
-	qdf_nbuf_t parent, next, frag_list;
+	qdf_nbuf_t parent, frag_list, next = NULL;
 	uint16_t frag_list_len = 0;
 	uint16_t mpdu_len;
 	bool last_nbuf;