Move kernel stats out of CPU and into XC.

arch/alpha/ev5.cc:
    Move kernel stats out of CPU and into XC.  Also be sure to check if the kernel stats exist prior to using them.

--HG--
extra : convert_revision : 565cd7026410fd7d8586f953d9b328c2e67a9473

cpu/simple/cpu.cc

@@ -782,7 +782,7 @@ SimpleCPU::tick()
 
 #if FULL_SYSTEM
         if (system->kernelBinning->fnbin) {
-            assert(kernelStats);
+            assert(cpuXC->getKernelStats());
             system->kernelBinning->execute(xcProxy, inst);
         }