mwifiex: change debug dump issue since skb maybe null

This patch fixes semantic warning for debugging data dump feature.
Previous code is based on the assumption that skb is not null.
New change makes sure that we already have data buffer.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NZhaoyang Liu <liuzy@marvell.com>
Signed-off-by: NAvinash Patil <patila@marvell.com>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/mwifiex/cmdevt.c

@@ -469,10 +469,11 @@ int mwifiex_process_event(struct mwifiex_adapter *adapter)
 		memset(rx_info, 0, sizeof(*rx_info));
 		rx_info->bss_num = priv->bss_num;
 		rx_info->bss_type = priv->bss_type;
+		mwifiex_dbg_dump(adapter, EVT_D, "Event Buf:",
+				 skb->data, skb->len);
 	}
 
 	mwifiex_dbg(adapter, EVENT, "EVENT: cause: %#x\n", eventcause);
-	mwifiex_dbg_dump(adapter, EVT_D, "Event Buf:", skb->data, skb->len);
 
 	if (priv->bss_role == MWIFIEX_BSS_ROLE_UAP)
 		ret = mwifiex_process_uap_event(priv);