systemc: Add SimObject::regStats to systemc kernel

Without this call, not all stats are registered correctly.

Change-Id: I81ff5305fdb8491c717c1ac2d41434d101c6ed3b
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/60252
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Matthias Jung <jungma@eit.uni-kl.de>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>

src/systemc/core/kernel.cc

@@ -85,6 +85,8 @@ Kernel::init()
 void
 Kernel::regStats()
 {
+    gem5::SimObject::regStats();
+
     if (scMainFiber.finished() || stopAfterCallbacks)
         return;