asink_anullsink: fix copyright

git blame says authors are:
     19 S.N. Hemanth Meenakshisundaram
      2 Reimar Döffinger

initial commit:
	commit f0a5543898
	Author: S.N. Hemanth Meenakshisundaram <smeenaks@ucsd.edu>
	Date:   Sat Sep 25 01:57:01 2010 +0000

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/asink_anullsink.c

@@ -1,4 +1,6 @@
 /*
+ * Copyright (c) 2010 S.N. Hemanth Meenakshisundaram <smeenaks@ucsd.edu>
+ *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or