Mark chroma_sample_position as deprecated

Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
diff --git a/va/va_dec_av1.h b/va/va_dec_av1.h
index 6122f1a..a1544bf 100644
--- a/va/va_dec_av1.h
+++ b/va/va_dec_av1.h
@@ -255,6 +255,7 @@
             uint32_t        color_range                                 : 1;
             uint32_t        subsampling_x                               : 1;
             uint32_t        subsampling_y                               : 1;
+            /** chroma_sampling_position is deprecated */
             uint32_t        chroma_sample_position                      : 1;
             uint32_t        film_grain_params_present                   : 1;
             /** \brief Reserved bytes for future use, must be zero */