netfilter: ip_tables: remove clusterip target

Marked as 'to be removed soon' since kernel 4.1 (2015).
Functionality was superseded by the 'cluster' match, added in kernel
2.6.30 (2009).

clusterip_tg_check still has races that can give

 proc_dir_entry 'ipt_CLUSTERIP/10.1.1.2' already registered

followed by a WARN splat.

Remove it instead of trying to fix this up again.
clusterip uapi header is left as-is for now.
Signed-off-by: Florian Westphal <fw@strlen.de>

net/ipv4/netfilter/Kconfig

@@ -259,20 +259,6 @@ config IP_NF_MANGLE
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
-config IP_NF_TARGET_CLUSTERIP
-	tristate "CLUSTERIP target support"
-	depends on IP_NF_MANGLE
-	depends on NF_CONNTRACK
-	depends on NETFILTER_ADVANCED
-	select NF_CONNTRACK_MARK
-	select NETFILTER_FAMILY_ARP
-	help
-	  The CLUSTERIP target allows you to build load-balancing clusters of
-	  network servers without having a dedicated load-balancing
-	  router/server/switch.
-
-	  To compile it as a module, choose M here.  If unsure, say N.
-
 config IP_NF_TARGET_ECN
 	tristate "ECN target support"
 	depends on IP_NF_MANGLE

net/ipv4/netfilter/Makefile

@@ -39,7 +39,6 @@ obj-$(CONFIG_IP_NF_MATCH_AH) += ipt_ah.o
 obj-$(CONFIG_IP_NF_MATCH_RPFILTER) += ipt_rpfilter.o
 
 # targets
-obj-$(CONFIG_IP_NF_TARGET_CLUSTERIP) += ipt_CLUSTERIP.o
 obj-$(CONFIG_IP_NF_TARGET_ECN) += ipt_ECN.o
 obj-$(CONFIG_IP_NF_TARGET_REJECT) += ipt_REJECT.o
 obj-$(CONFIG_IP_NF_TARGET_SYNPROXY) += ipt_SYNPROXY.o