Add an explicit conversion to int

To avoid unsigned int overflow

Change-Id: Ie070fea50b4b6c4a0e80c61371a2366dd79ed570

av1/encoder/temporal_filter.c

@@ -175,8 +175,8 @@ void av1_highbd_temporal_filter_apply_c(
 
       for (idy = -1; idy <= 1; ++idy) {
         for (idx = -1; idx <= 1; ++idx) {
-          int row = i + idy;
-          int col = j + idx;
+          int row = (int)i + idy;
+          int col = (int)j + idx;
 
           if (row >= 0 && row < (int)block_height && col >= 0 &&
               col < (int)block_width) {