iwlwifi: remove iwl_tx_queue declaration

The declaration isn't needed as the struct is only
used in code that includes the right header file.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>

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

@@ -51,8 +51,6 @@
 #include "iwl-op-mode.h"
 #include "iwl-notif-wait.h"
 
-struct iwl_tx_queue;
-
 /* CT-KILL constants */
 #define CT_KILL_THRESHOLD_LEGACY   110 /* in Celsius */
 #define CT_KILL_THRESHOLD	   114 /* in Celsius */