ip: cleanup typos in documentation

Type: style

Change-Id: I7d44b7fab1b8b196e4934cb4832ee51084c5bf98
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>
diff --git a/src/vnet/ip/ip.c b/src/vnet/ip/ip.c
index c5b43d4..785cd49 100644
--- a/src/vnet/ip/ip.c
+++ b/src/vnet/ip/ip.c
@@ -309,7 +309,7 @@
 #undef _
     }
 
-  return (format (s, "unknon"));
+  return (format (s, "unknown"));
 }
 
 /*