net/softnic: fix connection memory leak

In function softnic_conn_init(), a block of memory is allocated as
connection buffer, but it is never freed in softnic_conn_free(),
which cause memory leak.

Fixes: 7709a63bf178 ("net/softnic: add connection agent")
Cc: stable@dpdk.org

Signed-off-by: Dapeng Yu <dapengx.yu@intel.com>
Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>

drivers/net/softnic/conn.c

@@ -144,6 +144,7 @@ softnic_conn_free(struct softnic_conn *conn)
 
 	free(conn->msg_out);
 	free(conn->msg_in);
+	free(conn->buf);
 	free(conn->prompt);
 	free(conn->welcome);
 	free(conn);