Remove __stdcall warnings in ARM (KhronosGroup#302)

* Remove __stdcall warnings in x64 and ARM

* Refactor conditions

* Remove undef

* Apply corrections

Author: joselopeqti

CL/cl_platform.h

@@ -23,24 +23,20 @@
 extern "C" {
 #endif
 
-#if defined(_WIN32)
-    #if !defined(CL_API_ENTRY)
-        #define CL_API_ENTRY
-    #endif
-    #if !defined(CL_API_CALL)
-        #define CL_API_CALL     __stdcall
-    #endif
-    #if !defined(CL_CALLBACK)
-        #define CL_CALLBACK     __stdcall
-    #endif
-#else
-    #if !defined(CL_API_ENTRY)
-        #define CL_API_ENTRY
-    #endif
-    #if !defined(CL_API_CALL)
+#if !defined(CL_API_ENTRY)
+    #define CL_API_ENTRY
+#endif
+#if !defined(CL_API_CALL)
+    #if defined(_WIN32) && !defined(__aarch64__) && !defined(__arm64__)
+        #define CL_API_CALL __stdcall
+    #else
         #define CL_API_CALL
     #endif
-    #if !defined(CL_CALLBACK)
+#endif
+#if !defined(CL_CALLBACK)
+    #if defined(_WIN32) && !defined(__aarch64__) && !defined(__arm64__)
+        #define CL_CALLBACK __stdcall
+    #else
         #define CL_CALLBACK
     #endif
 #endif