arm: Get rid of using namespace std and TheISA in realview.cc.

Neither was actually used by the nearly empty file.

Change-Id: Ief1b77b18c8c616511bf9870e1667439a42dfcbd
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22266
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/arm/realview.cc

@@ -50,14 +50,10 @@
 #include <string>
 #include <vector>
 
-#include "config/the_isa.hh"
 #include "cpu/intr_control.hh"
 #include "dev/arm/base_gic.hh"
 #include "sim/system.hh"
 
-using namespace std;
-using namespace TheISA;
-
 
 RealView::RealView(const Params *p)
     : Platform(p), system(p->system), gic(nullptr)