vl: remove old, long-unused defines

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/vl.c b/vl.c
index a7b00cd..a7c3f8e 100644
--- a/vl.c
+++ b/vl.c
@@ -172,9 +172,6 @@
 #include "qapi/string-input-visitor.h"
 #include "qom/object_interfaces.h"
 
-//#define DEBUG_NET
-//#define DEBUG_SLIRP
-
 #define DEFAULT_RAM_SIZE 128
 
 #define MAX_VIRTIO_CONSOLES 1