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/simple_thread.hh

@@ -216,18 +216,14 @@ class SimpleThread : public ThreadState, public ThreadContext
     }
 
     PortProxy &getPhysProxy() override { return ThreadState::getPhysProxy(); }
-    FSTranslatingPortProxy &
-    getVirtProxy() override
-    {
-        return ThreadState::getVirtProxy();
-    }
+    PortProxy &getVirtProxy() override { return ThreadState::getVirtProxy(); }
 
     void initMemProxies(ThreadContext *tc) override
     {
         ThreadState::initMemProxies(tc);
     }
 
-    SETranslatingPortProxy &
+    PortProxy &
     getMemProxy() override
     {
         return ThreadState::getMemProxy();