axi_dmac: Fix src_reponse_fifo control signals

The src_response_fifo has been removed from the design, but we still need to
assert the ready and empty control signals for things to work properly.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

library/axi_dmac/request_arb.v

@@ -1012,6 +1012,8 @@ util_axis_fifo #(
 	.m_axis_ready(response_src_ready),
 	.m_axis_data(response_src_resp)
 );*/
+assign src_response_empty = 1'b1;
+assign src_response_ready = 1'b1;
 
 dmac_request_generator #(
 	.C_ID_WIDTH(C_ID_WIDTH),