BUILD: ssl: ssl_utils requires chunk.h

It uses chunk_printf() so it needs it. Currently it gets it through
others.
diff --git a/src/ssl_utils.c b/src/ssl_utils.c
index 0a12fea..cb94140 100644
--- a/src/ssl_utils.c
+++ b/src/ssl_utils.c
@@ -14,6 +14,7 @@
 
 #include <haproxy/api.h>
 #include <haproxy/buf-t.h>
+#include <haproxy/chunk.h>
 #include <haproxy/openssl-compat.h>
 #include <haproxy/ssl_sock.h>