iwlagn: simplify the iwl_device_cmd layout

This simplifies both the transport layer and the upper layer.

Kill the union in the device command, which avoids the funny syntax
we had: cmd->cmd.payload.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
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-agn-tx.c b/drivers/net/wireless/iwlwifi/iwl-agn-tx.c
index 4aa414a..abb702d 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-tx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-tx.c
@@ -322,7 +322,7 @@
 		goto drop_unlock_sta;
 
 	memset(dev_cmd, 0, sizeof(*dev_cmd));
-	tx_cmd = &dev_cmd->cmd.tx;
+	tx_cmd = (struct iwl_tx_cmd *) dev_cmd->payload;
 
 	/* Copy MAC header from skb into command buffer */
 	memcpy(tx_cmd->hdr, hdr, hdr_len);