stats: Get rid of some kernel stats related cruft.

The kernel stat mechanism should really be refactored and moved somewhere
else, but in the mean time there's some old cruft that can be cleared away.

Change-Id: I21e725de590dda0d20bf3bc675bbe976c7b1bd86
Reviewed-on: https://gem5-review.googlesource.com/4600
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

src/arch/alpha/kernel_stats.cc

@@ -50,8 +50,8 @@ namespace Kernel {
 
 const char *modestr[] = { "kernel", "user", "idle" };
 
-Statistics::Statistics(System *system)
-    : ::Kernel::Statistics(system),
+Statistics::Statistics()
+    : ::Kernel::Statistics(),
       idleProcess((Addr)-1), themode(kernel), lastModeTick(0)
 {
 }

src/arch/alpha/kernel_stats.hh

@@ -40,11 +40,7 @@
 #include "cpu/static_inst.hh"
 #include "kern/kernel_stats.hh"
 
-class BaseCPU;
 class ThreadContext;
-class FnEvent;
-// What does kernel stats expect is included?
-class System;
 
 namespace AlphaISA {
 namespace Kernel {
@@ -73,7 +69,7 @@ class Statistics : public ::Kernel::Statistics
     Stats::Scalar _swap_context;
 
   public:
-    Statistics(System *system);
+    Statistics();
 
     void regStats(const std::string &name);