Remove unused includes

Change-Id: Icc528c71ce0cdd6797445ecdbc4b43ade5c2620a
diff --git a/av1/encoder/x86/corner_match_avx2.c b/av1/encoder/x86/corner_match_avx2.c
index 3351d0a..7a3b999 100644
--- a/av1/encoder/x86/corner_match_avx2.c
+++ b/av1/encoder/x86/corner_match_avx2.c
@@ -9,10 +9,7 @@
  * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
  */
 
-#include <stdlib.h>
-#include <memory.h>
 #include <math.h>
-#include <assert.h>
 
 #include <immintrin.h>
 #include "config/av1_rtcd.h"