WinCE: fix vlc_GetCPUCount()

The function used by the Win32 implementation is not available, so just
leave it unimplemented.

src/misc/cpu.c

@@ -323,7 +323,7 @@ const struct
  */
 unsigned vlc_GetCPUCount(void)
 {
-#ifdef WIN32
+#if defined(WIN32) && !defined(UNDER_CE)
     DWORD process_mask;
     DWORD system_mask;
     if (!GetProcessAffinityMask(GetCurrentProcess(), &process_mask, &system_mask))