[NETFILTER]: xt_hashlimit: fix ip6tables dependency

IP6_NF_IPTABLES=m, CONFIG_NETFILTER_XT_MATCH_HASHLIMIT=y results in a
linker error since ipv6_find_hdr is defined in ip6_tables.c. Fix similar
to Adrian Bunk's H.323 conntrack patch: selecting ip6_tables to be build
as module requires hashlimit to be built as module as well.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netfilter/Kconfig

@@ -628,7 +628,7 @@ config NETFILTER_XT_MATCH_TCPMSS
 
 config NETFILTER_XT_MATCH_HASHLIMIT
 	tristate '"hashlimit" match support'
-	depends on NETFILTER_XTABLES
+	depends on NETFILTER_XTABLES && (IP6_NF_IPTABLES || IP6_NF_IPTABLES=n)
 	help
 	  This option adds a `hashlimit' match.