sim: Add a getPort function to SimObject.

This will retrieve a Port object from a given SimObject (which might
not be a MemObject) no matter what flavor of Port it is.

Change-Id: I636b85e9d4929a05a769e165849106bcb5f3e9c1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17037
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

src/python/m5/SimObject.py

@@ -1642,6 +1642,10 @@ class SimObject(object):
     def getValue(self):
         return self.getCCObject()
 
+    @cxxMethod(return_value_policy="reference")
+    def getPort(self, if_name, idx):
+        pass
+
     # Create C++ port connections corresponding to the connections in
     # _port_refs
     def connectPorts(self):