[hardware] Increase DMA buffer depth
With 4 tiles per DMA, we need to buffer four request to avoid creating
back pressure in one of the tiles.
@@ -517,7 +517,7 @@ module mempool_group
.IdWidth (AxiTileIdWidth ),
.AxReqFifoDepth (2 ),
.TransFifoDepth (1 ),
- .BufferDepth (3 ),
+ .BufferDepth (4 ),
.axi_req_t (axi_tile_req_t ),
.axi_res_t (axi_tile_resp_t),
.burst_req_t (dma_req_t ),
