v4l2videoenc: Remove dead code

gst_v4l2_object_stop() will free and nullify the pool, so the
following if will never be true.

https://bugzilla.gnome.org/show_bug.cgi?id=791338
diff --git a/sys/v4l2/gstv4l2videoenc.c b/sys/v4l2/gstv4l2videoenc.c
index 6be1bed..1783b86 100644
--- a/sys/v4l2/gstv4l2videoenc.c
+++ b/sys/v4l2/gstv4l2videoenc.c
@@ -218,11 +218,6 @@
   gst_v4l2_object_stop (self->v4l2output);
   gst_v4l2_object_stop (self->v4l2capture);
 
-  if (self->v4l2output->pool)
-    gst_v4l2_buffer_pool_flush (self->v4l2output->pool);
-  if (self->v4l2capture->pool)
-    gst_v4l2_buffer_pool_flush (self->v4l2capture->pool);
-
   if (self->input_state) {
     gst_video_codec_state_unref (self->input_state);
     self->input_state = NULL;