qcacmn: fix monitor nbuf double unmap when rmmod

When reaping rx monitor msdu in dp_rx_mon_mpdu_pop, if msdu_ppdu_id >
ppdu_id, then the corresbonding dp_rx_desc will not be added to free list,
and in_use flag still is 1 but it has done nbuf unmap which linked
to this rx desc. meantime, if rmmod triggered then it will go through the
rx desc pool and unmap the linked nbuf that in_use flag is 1, panic
happened. add unmapped flag checking to avoid double unmap.

CRs-fixed: 2201071

Change-Id: Idead32b189f513897deebf646b72585b257151c2

dp/wifi3.0/dp_rx_desc.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2017 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2016-2018 The Linux Foundation. All rights reserved.
  *
  * Permission to use, copy, modify, and/or distribute this software for
  * any purpose with or without fee is hereby granted, provided that the
@@ -81,7 +81,8 @@ void dp_rx_desc_pool_free(struct dp_soc *soc, uint32_t pool_id,
 	qdf_spin_lock_bh(&soc->rx_desc_mutex[pool_id]);
 	for (i = 0; i < rx_desc_pool->pool_size; i++) {
 		if (rx_desc_pool->array[i].rx_desc.in_use) {
-			qdf_nbuf_unmap_single(soc->osdev,
+			if (!(rx_desc_pool->array[i].rx_desc.unmapped))
+				qdf_nbuf_unmap_single(soc->osdev,
 					rx_desc_pool->array[i].rx_desc.nbuf,
 					QDF_DMA_BIDIRECTIONAL);
 			qdf_nbuf_free(rx_desc_pool->array[i].rx_desc.nbuf);