iwlwifi: do not use GFP_DMA in iwl_tx_queue_init

GFP_DMA is not necessary for the iwlwifi hardware and it can cause
allocation failures and/or invoke the OOM killer on lots of systems.

For reference:

	https://bugzilla.redhat.com/show_bug.cgi?id=459709Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -426,7 +426,7 @@ static int iwl_tx_queue_init(struct iwl_priv *priv,
 				continue;
 		}
 
-		txq->cmd[i] = kmalloc(len, GFP_KERNEL | GFP_DMA);
+		txq->cmd[i] = kmalloc(len, GFP_KERNEL);
 		if (!txq->cmd[i])
 			return -ENOMEM;
 	}