netfilter: fix Kconfig dependencies for nf_dup_ipv{4,6}

net/built-in.o: In function `nf_dup_ipv4': (.text+0xed24d): undefined reference to `nf_conntrack_untracked'
net/built-in.o: In function `nf_dup_ipv4': (.text+0xed267): undefined reference to `nf_conntrack_untracked'
net/built-in.o: In function `nf_dup_ipv6': (.text+0x158aef): undefined reference to `nf_conntrack_untracked'
net/built-in.o: In function `nf_dup_ipv6': (.text+0x158b09): undefined reference to `nf_conntrack_untracked'
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/Kconfig

@@ -75,6 +75,7 @@ endif # NF_TABLES
 
 config NF_DUP_IPV4
 	tristate "Netfilter IPv4 packet duplication to alternate destination"
+	depends on !NF_CONNTRACK || NF_CONNTRACK
 	help
 	  This option enables the nf_dup_ipv4 core, which duplicates an IPv4
 	  packet to be rerouted to another destination.

net/ipv6/netfilter/Kconfig

@@ -58,6 +58,7 @@ endif # NF_TABLES
 
 config NF_DUP_IPV6
 	tristate "Netfilter IPv6 packet duplication to alternate destination"
+	depends on !NF_CONNTRACK || NF_CONNTRACK
 	help
 	  This option enables the nf_dup_ipv6 core, which duplicates an IPv6
 	  packet to be rerouted to another destination.