iwlwifi: make iwl_tx_queue->tfds void*

Instead of having both tfds and tfds39, we can just have a void *tfds.
It makes the tx_queue structure nicer, and the code cleaner. It also helps
with further TX queues management code merging.

Signed-off-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-tx.c b/drivers/net/wireless/iwlwifi/iwl-tx.c
index 1a2cfbe..83e9f32 100644
--- a/drivers/net/wireless/iwlwifi/iwl-tx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-tx.c
@@ -295,12 +295,12 @@
 	/* Circular buffer of transmit frame descriptors (TFDs),
 	 * shared with device */
 	txq->tfds = pci_alloc_consistent(dev,
-			sizeof(txq->tfds[0]) * TFD_QUEUE_SIZE_MAX,
+			sizeof(struct iwl_tfd) * TFD_QUEUE_SIZE_MAX,
 			&txq->q.dma_addr);
 
 	if (!txq->tfds) {
 		IWL_ERR(priv, "pci_alloc_consistent(%zd) failed\n",
-			  sizeof(txq->tfds[0]) * TFD_QUEUE_SIZE_MAX);
+			  sizeof(struct iwl_tfd) * TFD_QUEUE_SIZE_MAX);
 		goto error;
 	}
 	txq->q.id = id;