fastmodel: Add in a missing include and namespace for itState.

Change-Id: I47661d95ae6f07768cb6ac1610bc29bc029c2bd9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25624
Reviewed-by: Chun-Chen TK Hsu <chunchenhsu@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/fastmodel/iris/thread_context.cc

@@ -29,6 +29,7 @@
 
 #include <utility>
 
+#include "arch/arm/utility.hh"
 #include "iris/detail/IrisCppAdapter.h"
 #include "iris/detail/IrisObjects.h"
 #include "mem/fs_translating_port_proxy.hh"
@@ -443,7 +444,7 @@ ThreadContext::pcState() const
     pc.aarch64(!cpsr.width);
     pc.nextAArch64(!cpsr.width);
     pc.illegalExec(false);
-    pc.itstate(itState(cpsr));
+    pc.itstate(ArmISA::itState(cpsr));
     pc.nextItstate(0);
 
     iris::ResourceReadResult result;