rtlwifi: check for array overflow

This is merged by Ping-Ke Shih from commit dc33bd43 ("staging:
rtlwifi: check for array overflow"), and the original commit log is
reserved below.

Smatch is distrustful of the "capab" value and marks it as user
controlled.  I think it actually comes from the firmware?  Anyway, I
looked at other drivers and they added a bounds check and it seems like
a harmless thing to have so I have added it here as well.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/realtek/rtlwifi/base.c

@@ -1321,6 +1321,10 @@ bool rtl_action_proc(struct ieee80211_hw *hw, struct sk_buff *skb, u8 is_tx)
 				  le16_to_cpu(mgmt->u.action.u.addba_req.capab);
 				tid = (capab &
 				       IEEE80211_ADDBA_PARAM_TID_MASK) >> 2;
+				if (tid >= MAX_TID_COUNT) {
+					rcu_read_unlock();
+					return true;
+				}
 				tid_data = &sta_entry->tids[tid];
 				if (tid_data->agg.rx_agg_state ==
 				    RTL_RX_AGG_START)