iwlagn: warn about nested SYNC commands

Since there is no protection around SYNC host command mechanism, at least WARN
when collision happens between two SYNC host comamnds. I am not sure there is a
real  issue (beyond the HCMD_ACTIVE flag maintenance) with having two SYNC host
commands at the same time, but at least now, we will know about it.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-dev.h b/drivers/net/wireless/iwlwifi/iwl-dev.h
index 34f9d0f..2d13d89 100644
--- a/drivers/net/wireless/iwlwifi/iwl-dev.h
+++ b/drivers/net/wireless/iwlwifi/iwl-dev.h
@@ -1300,6 +1300,7 @@
 
 	/* command queue number */
 	u8 cmd_queue;
+	u8 last_sync_cmd_id;
 
 	/* max number of station keys */
 	u8 sta_key_max_num;