sim: allow specifying remote gdb port for each workload

In a platform with multiple systems, we may want to specify the
remote gdb port for each system. This change makes it
possible to specify the port number at each Workload instance.

Change-Id: I755b3960ee920ae5289819aa05d98902614a5615
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/65151
Maintainer: Earl Ou <shunhsingou@google.com>
Reviewed-by: Yu-hsin Wang <yuhsingw@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/Workload.py

@@ -36,6 +36,9 @@ class Workload(SimObject):
     abstract = True
 
     wait_for_remote_gdb = Param.Bool(False, "Wait for a remote GDB connection")
+    remote_gdb_port = Param.Int(
+        7000, "Default port number used for remote GDB connection"
+    )
 
     @cxxMethod
     def sendToGdb(self, message):