iwlwifi: mvm: remove unused sta_id variable in iwl_mvm_change_queue_owner()

Remove the sta_id variable, to avoid this compile warning when
compiling with W=1:

/home/luca/iwlwifi/stack-dev/drivers/net/wireless/intel/iwlwifi/mvm/sta.c: In function ‘iwl_mvm_change_queue_owner’:
/home/luca/iwlwifi/stack-dev/drivers/net/wireless/intel/iwlwifi/mvm/sta.c:871:5: warning: variable ‘sta_id’ set but not used [-Wunused-but-set-variable]
  s8 sta_id;
     ^
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/sta.c

@@ -868,7 +868,6 @@ static void iwl_mvm_change_queue_owner(struct iwl_mvm *mvm, int queue)
 		.scd_queue = queue,
 		.action = SCD_CFG_UPDATE_QUEUE_TID,
 	};
-	s8 sta_id;
 	int tid;
 	unsigned long tid_bitmap;
 	int ret;
@@ -876,7 +875,6 @@ static void iwl_mvm_change_queue_owner(struct iwl_mvm *mvm, int queue)
 	lockdep_assert_held(&mvm->mutex);
 
 	spin_lock_bh(&mvm->queue_info_lock);
-	sta_id = mvm->queue_info[queue].ra_sta_id;
 	tid_bitmap = mvm->queue_info[queue].tid_bitmap;
 	spin_unlock_bh(&mvm->queue_info_lock);