netfilter: fix missing dependencies for NETFILTER_XT_MATCH_CONNLABEL

It was possible to set NF_CONNTRACK=n and NF_CONNTRACK_LABELS=y via
NETFILTER_XT_MATCH_CONNLABEL=y.

warning: (NETFILTER_XT_MATCH_CONNLABEL) selects NF_CONNTRACK_LABELS which has
unmet direct dependencies (NET && INET && NETFILTER && NF_CONNTRACK)

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/Kconfig

@@ -860,6 +860,7 @@ config NETFILTER_XT_MATCH_CONNBYTES
 config NETFILTER_XT_MATCH_CONNLABEL
 	tristate '"connlabel" match support'
 	select NF_CONNTRACK_LABELS
+	depends on NF_CONNTRACK
 	depends on NETFILTER_ADVANCED
 	---help---
 	  This match allows you to test and assign userspace-defined labels names