ecp5: Fix dynamic DELAYF control

Signed-off-by: David Shah <dave@ds0.me>

ecp5/bitstream.cc

diff --git a/ecp5/bitstream.cc b/ecp5/bitstream.cc
index 9732cd5..b491bf7 100644
--- a/ecp5/bitstream.cc
+++ b/ecp5/bitstream.cc
@@ -1293,6 +1293,9 @@
                 else
                     cc.tiles[pic_tile].add_enum(prim + "." + param.first.str(ctx), param.second.as_string());
             }
+            if (get_net_or_empty(ci, id_LOADN) != nullptr) {
+                cc.tiles[pic_tile].add_enum(prim + ".LOADNMUX", "LOADN");
+            }
         } else if (ci->type == id_DCUA) {
             TileGroup tg;
             tg.tiles = get_dcu_tiles(ctx, ci->bel);