style: [patch 3/22] reduce include dependencies in some headers

Used cppclean to help identify useless includes and removed them. This
involved erroneously included headers, but also cases where forward
declarations could have been used rather than a full include.

src/sim/process.hh

@@ -34,6 +34,7 @@
 #define __PROCESS_HH__
 
 #include <array>
+#include <map>
 #include <string>
 #include <vector>
 
@@ -44,15 +45,16 @@
 #include "mem/se_translating_port_proxy.hh"
 #include "sim/fd_entry.hh"
 #include "sim/sim_object.hh"
-#include "sim/syscall_return.hh"
 
-class PageTable;
-struct ProcessParams;
 struct LiveProcessParams;
+struct ProcessParams;
+
+class EmulatedDriver;
+class PageTableBase;
 class SyscallDesc;
+class SyscallReturn;
 class System;
 class ThreadContext;
-class EmulatedDriver;
 
 template<class IntType>
 struct AuxVector