ControllerInterface: Switch to std::shared_ptr

Small cleanup by using std::shared_ptr and getting rid of
ciface.Devices() which just returned the m_devices (which defeats the
point of making m_devices protected).

Incidentally, this should make the code safer when we have
different threads accessing devices in the future (for hotplug?).

A lot of code use Device references directly so there is
no easy way to remove FindDevice() and make those unique_ptrs.

Source/Core/InputCommon/ControllerInterface/Pipes/Pipes.cpp

@@ -61,7 +61,7 @@ void Init()
     int fd = open(child.physicalName.c_str(), O_RDONLY | O_NONBLOCK);
     if (fd < 0)
       continue;
-    g_controller_interface.AddDevice(new PipeDevice(fd, child.virtualName, found++));
+    g_controller_interface.AddDevice(std::make_shared<PipeDevice>(fd, child.virtualName, found++));
   }
 }