plugins: mark a few more functions as internal.

Mark the following functions are internal, i.e. private to the vaapi plug-in:
- gst_vaapi_video_buffer_pool_get_type()
- gst_vaapi_video_converter_glx_get_type()
- gst_vaapi_video_converter_glx_new()

gst/vaapi/gstvaapivideobufferpool.h

@@ -79,6 +79,7 @@ struct _GstVaapiVideoBufferPoolClass {
     GstBufferPoolClass parent_class;
 };
 
+G_GNUC_INTERNAL
 GType
 gst_vaapi_video_buffer_pool_get_type(void) G_GNUC_CONST;
 

gst/vaapi/gstvaapivideoconverter_glx.h

@@ -79,9 +79,11 @@ struct _GstVaapiVideoConverterGLXClass {
     GObjectClass parent_class;
 };
 
+G_GNUC_INTERNAL
 GType
 gst_vaapi_video_converter_glx_get_type(void) G_GNUC_CONST;
 
+G_GNUC_INTERNAL
 GstSurfaceConverter *
 gst_vaapi_video_converter_glx_new(GstBuffer *buffer, const gchar *type,
     GValue *dest);