proresdec: fix decode_slice() prototype

Make the function prototype match the argument of
AVCodecCntext.execute() and remove the cast hiding
this mismatch.
Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/proresdec.c

@@ -499,8 +499,9 @@ static void decode_slice_plane(ProresContext *ctx, ProresThreadData *td,
 }
 
 
-static int decode_slice(AVCodecContext *avctx, ProresThreadData *td)
+static int decode_slice(AVCodecContext *avctx, void *tdata)
 {
+    ProresThreadData *td = tdata;
     ProresContext *ctx = avctx->priv_data;
     int mb_x_pos  = td->x_pos;
     int mb_y_pos  = td->y_pos;
@@ -621,7 +622,7 @@ static int decode_picture(ProresContext *ctx, int pic_num,
         }
     }
 
-    return avctx->execute(avctx, (void *) decode_slice,
+    return avctx->execute(avctx, decode_slice,
                           ctx->slice_data, NULL, slice_num,
                           sizeof(ctx->slice_data[0]));
 }