Remove unnecessary check for frame parallel decode.

The check will make the code break out from the loop earlier.
But without the check. it works the same in non frame-parallel decode.
In frame parallel decode, this check is wrong as there may be left
frames inside the decoder even if there are no more frames to read.
So the loop should continue until got_data = 0.

Change-Id: I42937cec5d80d1d921a008d78dafce0928c727e0

vpxdec.c

@@ -934,8 +934,6 @@ int main_loop(int argc, const char **argv_) {
       }
     }
 
-    if (stop_after && frame_in >= stop_after)
-      break;
   }
 
   if (summary || progress) {