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-sta.c b/drivers/net/wireless/iwlwifi/iwl-sta.c
index 7028f90..580a4d7 100644
--- a/drivers/net/wireless/iwlwifi/iwl-sta.c
+++ b/drivers/net/wireless/iwlwifi/iwl-sta.c
@@ -127,7 +127,7 @@
 {
 	struct iwl_rx_packet *pkt = rxb_addr(rxb);
 	struct iwl_addsta_cmd *addsta =
-		(struct iwl_addsta_cmd *)cmd->cmd.payload;
+		(struct iwl_addsta_cmd *) cmd->payload;
 
 	return iwl_process_add_sta_resp(priv, addsta, pkt);
 }