mwifiex: fix large amsdu packets causing firmware hang

Sometimes host prepares and downloads a large amsdu packet to firmware
which leads to a memory corruption in firmware.
The reason is __dev_alloc_skb() may allocate larger buffer than required
size. This patch solves the problem by checking "adapter->tx_buf_size"
instead of relying on skb_tailroom().
Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/marvell/mwifiex/11n_aggr.c

@@ -205,7 +205,8 @@ mwifiex_11n_aggregate_pkt(struct mwifiex_private *priv,
 
 	do {
 		/* Check if AMSDU can accommodate this MSDU */
-		if (skb_tailroom(skb_aggr) < (skb_src->len + LLC_SNAP_LEN))
+		if ((skb_aggr->len + skb_src->len + LLC_SNAP_LEN) >
+		    adapter->tx_buf_size)
 			break;
 
 		skb_src = skb_dequeue(&pra_list->skb_head);