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>
diff --git a/drivers/net/wireless/iwlwifi/iwl-trans-pcie-tx.c b/drivers/net/wireless/iwlwifi/iwl-trans-pcie-tx.c
index fa2ce39..fec7065 100644
--- a/drivers/net/wireless/iwlwifi/iwl-trans-pcie-tx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-trans-pcie-tx.c
@@ -636,6 +636,8 @@
 	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;