cpu, sim: Return PortProxy &s from all the proxy accessors.

This is a step towards merging the accessors for SE and FS modes.

Change-Id: I76818ab88b97097ac363e243be9cc1911b283090
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18579
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

src/cpu/thread_state.hh

@@ -47,6 +47,9 @@ namespace Kernel {
 
 class Checkpoint;
 
+class FSTranslatingPortProxy;
+class SETranslatingPortProxy;
+
 /**
  *  Struct for holding general thread state that is needed across CPU
  *  models.  This includes things such as pointers to the process,
@@ -100,7 +103,7 @@ struct ThreadState : public Serializable {
 
     PortProxy &getPhysProxy();
 
-    FSTranslatingPortProxy &getVirtProxy();
+    PortProxy &getVirtProxy();
 
     Process *getProcessPtr() { return process; }
 
@@ -119,7 +122,7 @@ struct ThreadState : public Serializable {
         }
     }
 
-    SETranslatingPortProxy &getMemProxy();
+    PortProxy &getMemProxy();
 
     /** Reads the number of instructions functionally executed and
      * committed.