netlabel: Kconfig: Update reference for NetLabel Tools project

The NetLabel Tools project has moved from http://netlabel.sf.net to a
GitHub project. Update to directly refer to the new home for the tools.
Signed-off-by: NSalvatore Bonaccorso <carnil@debian.org>
Acked-by: NPaul Moore <paul@paul-moore.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netlabel/Kconfig

@@ -14,6 +14,6 @@ config NETLABEL
 	  Documentation/netlabel as well as the NetLabel SourceForge project
 	  for configuration tools and additional documentation.
 
-	   * http://netlabel.sf.net
+	   * https://github.com/netlabel/netlabel_tools
 
 	  If you are unsure, say N.