cpu: Narrow the dependencies of the StaticInst class.

Include only the minimal number of headers to make StaticInst subclasses
easier to test with unit tests.

Change-Id: Ie2e1c01b77d1776b366d29982e481d62b6a2b8cf
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42965
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>

src/cpu/static_inst.hh

@@ -43,19 +43,17 @@
 #define __CPU_STATIC_INST_HH__
 
 #include <bitset>
+#include <cstdint>
 #include <memory>
 #include <string>
 
-#include "arch/registers.hh"
 #include "arch/types.hh"
 #include "base/logging.hh"
 #include "base/refcnt.hh"
-#include "base/types.hh"
 #include "config/the_isa.hh"
 #include "cpu/op_class.hh"
 #include "cpu/reg_class.hh"
 #include "cpu/static_inst_fwd.hh"
-#include "cpu/thread_context.hh"
 #include "enums/StaticInstFlags.hh"
 #include "sim/byteswap.hh"
 
@@ -63,6 +61,7 @@
 class Packet;
 
 class ExecContext;
+class ThreadContext;
 
 namespace Loader
 {