onepad: Remove use of "using namespace std"

"using namespace std" was causing ambiguity issues and compile errors on
FreeBSD. Remove it.

plugins/onepad/controller.cpp

@@ -31,7 +31,7 @@ __forceinline int get_keyboard_key(int pad, int keysym)
 {
     // You must use find instead of []
     // [] will create an element if the key does not exist and return 0
-    map<u32, u32>::iterator it = g_conf.keysym_map[pad].find(keysym);
+    std::map<u32, u32>::iterator it = g_conf.keysym_map[pad].find(keysym);
     if (it != g_conf.keysym_map[pad].end())
         return it->second;
     else

plugins/onepad/controller.h

@@ -50,7 +50,7 @@ public:
     };
 
     u32 log;
-    map<u32, u32> keysym_map[GAMEPAD_NUMBER];
+    std::map<u32, u32> keysym_map[GAMEPAD_NUMBER];
     std::array<size_t, GAMEPAD_NUMBER> unique_id;
     std::vector<std::string> sdl2_mapping;
 

plugins/onepad/onepad.h

@@ -46,7 +46,6 @@
 #include <memory>
 #include <mutex>
 #include <queue>
-using namespace std;
 
 #define PADdefs
 #include "PS2Edefs.h"