Fixed packet I/O in p4-14 programs

Tested on BMv2 and working

Change-Id: I834d7b5a8627181c6888500545e1bdbfe9af8dc1
diff --git a/tools/test/p4src/p4-14/include/parser.p4 b/tools/test/p4src/p4-14/include/parser.p4
index 73dcdfd..0223297 100644
--- a/tools/test/p4src/p4-14/include/parser.p4
+++ b/tools/test/p4src/p4-14/include/parser.p4
@@ -11,11 +11,12 @@
 header udp_t udp;
 
 parser start {
-    // FIXME: Cheat the compiler to generate the deparser of packet in
-    // This is just a hack, we assume first 8 bit of etherType won't be 0
-    return select( current(96, 8) ) {
-        NULL_ETH_TYPE : parse_pkt_in;
-        default       : default_parser;
+    // Hack to force deparsing of packet_in hdr.
+    // We assume it's impossible to receive a pkt with the first 8 bits of etherType 0.
+    // p4c-tofino complains when switching over 16 bits, i.e. the full etherType
+    return select(current(96, 8)) {
+        0 : parse_pkt_in;
+        default  : default_parser;
     }
 }