core_cpu: Make arm_interface instances a std::unique_ptr

This is only exposed by reference, so we can just make it a unique
pointer to get rid of the need to also use reference counting for the
pointer.

src/core/core_cpu.cpp

@@ -55,13 +55,13 @@ Cpu::Cpu(std::shared_ptr<ExclusiveMonitor> exclusive_monitor,
 
     if (Settings::values.use_cpu_jit) {
 #ifdef ARCHITECTURE_x86_64
-        arm_interface = std::make_shared<ARM_Dynarmic>(exclusive_monitor, core_index);
+        arm_interface = std::make_unique<ARM_Dynarmic>(exclusive_monitor, core_index);
 #else
-        arm_interface = std::make_shared<ARM_Unicorn>();
+        arm_interface = std::make_unique<ARM_Unicorn>();
         LOG_WARNING(Core, "CPU JIT requested, but Dynarmic not available");
 #endif
     } else {
-        arm_interface = std::make_shared<ARM_Unicorn>();
+        arm_interface = std::make_unique<ARM_Unicorn>();
     }
 
     scheduler = std::make_shared<Kernel::Scheduler>(*arm_interface);

src/core/core_cpu.h

@@ -76,7 +76,7 @@ public:
 private:
     void Reschedule();
 
-    std::shared_ptr<ARM_Interface> arm_interface;
+    std::unique_ptr<ARM_Interface> arm_interface;
     std::shared_ptr<CpuBarrier> cpu_barrier;
     std::shared_ptr<Kernel::Scheduler> scheduler;