power: Fix regStats for PowerModel and PowerModelState

Every Stats::Group need to call the parent regStats to
make sure that the base Stats::Group::regStats() gets
called

JIRA: https://gem5.atlassian.net/projects/GEM5/issues/GEM5-319

Change-Id: I931941d8ec5f375f7e51e719d43ae31af095f661
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26643
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/power/power_model.hh

@@ -84,6 +84,8 @@ class PowerModelState : public SimObject
     }
 
     void regStats() {
+        SimObject::regStats();
+
         dynamicPower
           .method(this, &PowerModelState::getDynamicPower)
           .name(params()->name + ".dynamic_power")
@@ -135,6 +137,8 @@ class PowerModel : public SimObject
     double getStaticPower() const;
 
     void regStats() {
+        SimObject::regStats();
+
         dynamicPower
           .method(this, &PowerModel::getDynamicPower)
           .name(params()->name + ".dynamic_power")