Remove unused Kconfig files

extensions/pknock/xt_pknock.Kconfig

@@ -1,13 +0,0 @@
-config NETFILTER_XT_MATCH_PKNOCK
-	tristate "Port knocking match support"
-	depends on NETFILTER_XTABLES && CONNECTOR
-	---help---
-	pknock match implements so-called Port Knocking, a stealthy system
-	for network authentication: client sends packets to selected, closed
-	ports on target machine in a specific sequence. The target machine
-	(which has pknock match rule set up) then decides whether to
-	unblock or block (again) its protected port with listening
-	service. This can be, for instance, used to avoid brute force attacks
-	on ssh or ftp services.
-
-	For more informations go to: http://portknocko.berlios.de/