dataflow_cpp: changed return type of operator >> to allow for connection chains

dataflow_cpp/include/embb/dataflow/internal/process.h

@@ -102,8 +102,9 @@ class Process< Slices, Serial, Inputs<Slices, I1, I2, I3, I4, I5>,
   }
 
   template <typename T>
-  void operator >> (T & target) {
+  T & operator >> (T & target) {
     GetOutput<0>() >> target.template GetInput<0>();
+    return target;
   }
 
   virtual void OnClock(int clock) {

dataflow_cpp/include/embb/dataflow/internal/select.h

@@ -105,8 +105,9 @@ class Select
   }
 
   template <typename T>
-  void operator >> (T & target) {
+  T & operator >> (T & target) {
     GetOutput<0>() >> target.template GetInput<0>();
+    return target;
   }
 
   virtual void OnClock(int clock) {

dataflow_cpp/include/embb/dataflow/internal/source.h

@@ -81,8 +81,9 @@ class Source< Slices, Outputs<Slices, O1, O2, O3, O4, O5> >
   }
 
   template <typename T>
-  void operator >> (T & target) {
+  T & operator >> (T & target) {
     GetOutput<0>() >> target.template GetInput<0>();
+    return target;
   }
 
  private:

dataflow_cpp/include/embb/dataflow/internal/switch.h

@@ -103,8 +103,9 @@ class Switch
   }
 
   template <typename T>
-  void operator >> (T & target) {
+  T & operator >> (T & target) {
     GetOutput<0>() >> target.template GetInput<0>();
+    return target;
   }
 
   virtual void OnClock(int clock) {