cpu: Don't forward declare RefCountingPtr

RefCountingPtr is sometimes forward declared to avoid having to
include refcnt.hh. This does not work since we typically return
instances of RefCountingPtr rather than references to instances. The
only reason this currently works is that we include refcnt.hh in
cprintf.hh, which "leaks" the header to most other source files. This
changeset replaces such forward declarations with an include of
refcnt.hh.

src/cpu/static_inst_fwd.hh

@@ -31,8 +31,9 @@
 #ifndef __CPU_STATIC_INST_FWD_HH__
 #define __CPU_STATIC_INST_FWD_HH__
 
+#include "base/refcnt.hh"
+
 class StaticInst;
-template <class T> class RefCountingPtr;
 typedef RefCountingPtr<StaticInst> StaticInstPtr;
 
 #endif // __CPU_STATIC_INST_FWD_HH__