mwifiex: fix smatch errors

drivers/net/wireless/mwifiex/main.c +828 mwifiex_remove_card(52)
  error: potential null derefence 'priv'.
drivers/net/wireless/mwifiex/main.c +828 mwifiex_remove_card(52)
  error: we previously assumed 'priv' could be null (see line 820)
drivers/net/wireless/mwifiex/txrx.c +90 mwifiex_process_tx(24)
  error: potential null derefence 'local_tx_pd'.
drivers/net/wireless/mwifiex/sta_ioctl.c +766
mwifiex_rate_ioctl_set_rate_value(30)
  error: buffer overflow 'rate' 14 <= 14

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mwifiex/main.c

@@ -825,6 +825,10 @@ int mwifiex_remove_card(struct mwifiex_adapter *adapter, struct semaphore *sem)
 		rtnl_unlock();
 	}
 
+	priv = adapter->priv[0];
+	if (!priv)
+		goto exit_remove;
+
 	wiphy_unregister(priv->wdev->wiphy);
 	wiphy_free(priv->wdev->wiphy);
 	kfree(priv->wdev);

drivers/net/wireless/mwifiex/sta_ioctl.c

@@ -763,7 +763,7 @@ static int mwifiex_rate_ioctl_set_rate_value(struct mwifiex_private *priv,
 			if ((rate[i] & 0x7f) == (rate_cfg->rate & 0x7f))
 				break;
 		}
-		if (!rate[i] || (i == MWIFIEX_SUPPORTED_RATES)) {
+		if ((i == MWIFIEX_SUPPORTED_RATES) || !rate[i]) {
 			dev_err(adapter->dev, "fixed data rate %#x is out "
 			       "of range\n", rate_cfg->rate);
 			return -1;

drivers/net/wireless/mwifiex/txrx.c

@@ -87,7 +87,8 @@ int mwifiex_process_tx(struct mwifiex_private *priv, struct sk_buff *skb,
 			(adapter->pps_uapsd_mode) &&
 			(adapter->tx_lock_flag)) {
 				priv->adapter->tx_lock_flag = false;
-				local_tx_pd->flags = 0;
+				if (local_tx_pd)
+					local_tx_pd->flags = 0;
 		}
 		dev_dbg(adapter->dev, "data: -EBUSY is returned\n");
 		break;