pps_gen: missing signal assignments when ext reference disabled

When external reference support was disabled, this was causing Altera-based
board (VFC-HD) never to generate valid timestamps for frames (pps-gen was never
producing pps_valid=1).

modules/wr_pps_gen/wr_pps_gen.vhd

@@ -257,7 +257,9 @@ begin  -- behavioral
   end process;
 
   gen_without_external_clock_input : if(not g_with_ext_clock_input) generate
-    ext_sync_p <= '0';
+    ext_sync_p        <= '0';
+    sync_in_progress  <= '0';
+    ppsg_escr_sync_in <= '0';
   end generate gen_without_external_clock_input;
 
   gen_with_external_clock_input : if(g_with_ext_clock_input) generate