simplify vp9_loop_filter_worker signature

use the type names directly in the function declaration rather than
(void *arg1, void *arg2)

Change-Id: I36bfc9c886310ce370bf0ca7c679ebd6e95109cc

vp9/common/vp9_loopfilter.c

@@ -1247,9 +1247,8 @@ void vp9_loop_filter_frame(YV12_BUFFER_CONFIG *frame,
                        y_only);
 }
 
-int vp9_loop_filter_worker(void *arg1, void *arg2) {
-  LFWorkerData *const lf_data = (LFWorkerData*)arg1;
-  (void)arg2;
+int vp9_loop_filter_worker(LFWorkerData *const lf_data, void *unused) {
+  (void)unused;
   vp9_loop_filter_rows(lf_data->frame_buffer, lf_data->cm, lf_data->planes,
                        lf_data->start, lf_data->stop, lf_data->y_only);
   return 1;

vp9/common/vp9_loopfilter.h

@@ -129,8 +129,8 @@ typedef struct LoopFilterWorkerData {
   int num_lf_workers;
 } LFWorkerData;
 
-// Operates on the rows described by LFWorkerData passed as 'arg1'.
-int vp9_loop_filter_worker(void *arg1, void *arg2);
+// Operates on the rows described by 'lf_data'.
+int vp9_loop_filter_worker(LFWorkerData *const lf_data, void *unused);
 #ifdef __cplusplus
 }  // extern "C"
 #endif