Refactor GridEvenShare::total_tiles to int32.

This value will always be representable with an int, and all usages
of it treat it as a 32-bit int. Changing the type avoids some casts
at usage sites.

cub/grid/grid_even_share.cuh

@@ -78,7 +78,7 @@ struct GridEvenShare
 {
 private:
 
-    OffsetT     total_tiles;
+    int         total_tiles;
     int         big_shares;
     OffsetT     big_share_items;
     OffsetT     normal_share_items;
@@ -130,11 +130,11 @@ public:
         this->block_offset          = num_items_;    // Initialize past-the-end
         this->block_end             = num_items_;    // Initialize past-the-end
         this->num_items             = num_items_;
-        this->total_tiles           = cub::DivideAndRoundUp(num_items_, tile_items);
-        this->grid_size             = CUB_MIN(static_cast<int>(total_tiles), max_grid_size);
-        OffsetT avg_tiles_per_block = total_tiles / grid_size;
-        // leftover grains go to big blocks
-        this->big_shares = static_cast<int>(total_tiles - (avg_tiles_per_block * grid_size));
+        this->total_tiles           = static_cast<int>(cub::DivideAndRoundUp(num_items_, tile_items));
+        this->grid_size             = CUB_MIN(total_tiles, max_grid_size);
+        int avg_tiles_per_block     = total_tiles / grid_size;
+        // leftover grains go to big blocks:
+        this->big_shares            = total_tiles - (avg_tiles_per_block * grid_size);
         this->normal_share_items    = avg_tiles_per_block * tile_items;
         this->normal_base_offset    = big_shares * tile_items;
         this->big_share_items       = normal_share_items + tile_items;