core/icmp: Revert to SyncFIFO for now until PacketFIFO regression is investigated.

liteeth/core/icmp.py

@@ -129,10 +129,10 @@ class LiteEthICMPEcho(Module):
 
         # # #
 
-        self.submodules.buffer = PacketFIFO(eth_icmp_user_description(dw),
-            payload_depth = 128//(dw//8),
-            param_depth   = 1,
-            buffered      = True
+        self.submodules.buffer = stream.SyncFIFO(
+            eth_icmp_user_description(dw),
+            128 // (dw // 8),
+            buffered=True
         )
         self.comb += [
             sink.connect(self.buffer.sink),