iwlwifi: do not set the sequence control bit is not needed

Check the IEEE80211_TX_CTL_ASSIGN_SEQ flag from mac80211, then decide how to
set the TX_CMD_FLG_SEQ_CTL_MSK bit. Setting the wrong bit in BAR frame whill
make the firmware to increment the sequence number which is incorrect and
cause unknown behavior.

CC: stable@vger.kernel.org #3.0+
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn-tx.c

@@ -91,7 +91,10 @@ static void iwlagn_tx_cmd_build_basic(struct iwl_priv *priv,
 		tx_cmd->tid_tspec = qc[0] & 0xf;
 		tx_flags &= ~TX_CMD_FLG_SEQ_CTL_MSK;
 	} else {
+		if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ)
 			tx_flags |= TX_CMD_FLG_SEQ_CTL_MSK;
+		else
+			tx_flags &= ~TX_CMD_FLG_SEQ_CTL_MSK;
 	}
 
 	iwlagn_tx_cmd_protection(priv, info, fc, &tx_flags);