egl: fix _EGL_NATIVE_PLATFORM fallback

When the X11 or Haiku platforms were compiled in, they would bypass the
`_EGL_NATIVE_PLATFORM` fallback by always returning themselves instead.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/egl/main/egldisplay.c

@@ -138,15 +138,6 @@ _eglNativePlatformDetectNativeDisplay(void *nativeDisplay)
       if (first_pointer == gbm_create_device)
          return _EGL_PLATFORM_DRM;
 #endif
-
-#ifdef HAVE_X11_PLATFORM
-      /* If not matched to any other platform, fallback to x11. */
-      return _EGL_PLATFORM_X11;
-#endif
-
-#ifdef HAVE_HAIKU_PLATFORM
-      return _EGL_PLATFORM_HAIKU;
-#endif
    }
 
    return _EGL_INVALID_PLATFORM;