iwlagn: add REPLY_ECHO host command

Add "echo" host command for testing and drebugging to make sure uCode still
responding

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-commands.h

@@ -89,6 +89,7 @@ struct iwl_priv;
 enum {
 	REPLY_ALIVE = 0x1,
 	REPLY_ERROR = 0x2,
+	REPLY_ECHO = 0x3,		/* test command */
 
 	/* RXON and QOS commands */
 	REPLY_RXON = 0x10,