cpu: fix simInsts and simOps not resetting (#1615)

This PR fixes the bug where simInsts and simOps don't reset when
m5.stats.reset() is called. The stats hostInstRate and hostOpRate are
affected by this change as well, as they depend on simInsts and simOps
respectively.

This is related to issue 1443 linked
[here](https://github.com/gem5/gem5/issues/1443).

src/cpu/base.cc

@@ -859,13 +859,13 @@ BaseCPU::GlobalStats::GlobalStats(statistics::Group *parent)
              "Simulator op (including micro ops) rate (op/s)")
 {
     simInsts
-        .functor(BaseCPU::numSimulatedInsts)
+        .functor(BaseCPU::GlobalStats::numSimulatedInsts)
         .precision(0)
         .prereq(simInsts)
         ;
 
     simOps
-        .functor(BaseCPU::numSimulatedOps)
+        .functor(BaseCPU::GlobalStats::numSimulatedOps)
         .precision(0)
         .prereq(simOps)
         ;