netfilter: xtables: fix up kconfig dependencies

Randy Dunlap reports arptables build failure:
arp_tables.c:(.text+0x20): undefined reference to `xt_find_table'

... because recent change removed a 'select' on the xtables core.
Add a "depends" clause on arptables to resolve this.

Kernel test robot reports another build breakage:
iptable_nat.c:(.text+0x8): undefined reference to `ipt_unregister_table_exit'

... because of a typo, the nat table selected ip6tables.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Closes: https://lore.kernel.org/netfilter-devel/d0dfbaef-046a-4c42-9daa-53636664bf6d@infradead.org/
Fixes: a9525c7f ("netfilter: xtables: allow xtables-nft only builds")
Fixes: 4654467d ("netfilter: arptables: allow xtables-nft only builds")
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Florian Westphal <fw@strlen.de>

net/ipv4/netfilter/Kconfig

@@ -217,7 +217,7 @@ config IP_NF_NAT
 	default m if NETFILTER_ADVANCED=n
 	select NF_NAT
 	select NETFILTER_XT_NAT
-	select IP6_NF_IPTABLES_LEGACY
+	select IP_NF_IPTABLES_LEGACY
 	help
 	  This enables the `nat' table in iptables. This allows masquerading,
 	  port forwarding and other forms of full Network Address Port
@@ -329,6 +329,7 @@ config NFT_COMPAT_ARP
 config IP_NF_ARPFILTER
 	tristate "arptables-legacy packet filtering support"
 	select IP_NF_ARPTABLES
+	depends on NETFILTER_XTABLES
 	help
 	  ARP packet filtering defines a table `filter', which has a series of
 	  rules for simple ARP packet filtering at local input and