utils/convolvtest: Remove uneeded libosmocore dependency

Change-Id: I1742146c31cadec8ce8afbbdae5777f076b212d4
diff --git a/utils/convolvetest/main.c b/utils/convolvetest/main.c
index ff88ba5..f4a76c3 100644
--- a/utils/convolvetest/main.c
+++ b/utils/convolvetest/main.c
@@ -1,6 +1,6 @@
 #include <stdio.h>
 #include <string.h>
-#include <osmocom/core/utils.h>
+#include <stdlib.h>
 #include "../../Transceiver52M/common/convolve.h"
 
 #define TESTVEC_LEN 1000