iwlagn: do nothing when disable agg in wrong state

When disable aggregation request come in on wrong agg state. ignore it
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-trans-pcie-tx.c

@@ -636,6 +636,8 @@ int iwl_trans_pcie_tx_agg_disable(struct iwl_trans *trans,
 	default:
 		IWL_WARN(trans, "Stopping AGG while state not ON"
 				"or starting\n");
+		spin_unlock_irqrestore(&trans->shrd->sta_lock, flags);
+		return 0;
 	}
 
 	write_ptr = trans_pcie->txq[txq_id].q.write_ptr;