add matrix_coefficients into VADecPictureParameterBufferAV1

Signed-off-by: Carl Zhang <carl.zhang@intel.com>
diff --git a/va/va_dec_av1.h b/va/va_dec_av1.h
index 31d4349..56bfb40 100755
--- a/va/va_dec_av1.h
+++ b/va/va_dec_av1.h
@@ -233,6 +233,9 @@
      */
     uint8_t                 bit_depth_idx;
 
+    /** \brief corresponds to AV1 spec variable of the same name. */
+    uint8_t                 matrix_coefficients;
+
     union {
         struct {
             uint32_t        still_picture                               : 1;