Read mode to mi->bmi for sub 8x8 blocks

Previously, only the motion vectors were being stored. This caused
a mismatch in the global motion experiment, which needs this
mode information to decide whether or not to use the gm parameters
in reconstruction.

Change-Id: I58cde750ec06587dbfb8d65b07c15a67b7d6b1f6

av1/decoder/decodemv.c

@@ -1454,6 +1454,7 @@ static void read_inter_block_mode_info(AV1Decoder *const pbi,
         };
 
         mi->bmi[j].as_mv[0].as_int = block[0].as_int;
+        mi->bmi[j].as_mode = b_mode;
         if (is_compound) mi->bmi[j].as_mv[1].as_int = block[1].as_int;
 
         if (num_4x4_h == 2) mi->bmi[j + 2] = mi->bmi[j];