netfilter: add back NETFILTER_XTABLES dependencies

Some Kconfig symbols were changed to depend on the 'bool' symbol
NETFILTER_XTABLES_LEGACY, which means they can now be set to built-in
when the xtables code itself is in a loadable module:

x86_64-linux-ld: vmlinux.o: in function `arpt_unregister_table_pre_exit':
(.text+0x1831987): undefined reference to `xt_find_table'
x86_64-linux-ld: vmlinux.o: in function `get_info.constprop.0':
arp_tables.c:(.text+0x1831aab): undefined reference to `xt_request_find_table_lock'
x86_64-linux-ld: arp_tables.c:(.text+0x1831bea): undefined reference to `xt_table_unlock'
x86_64-linux-ld: vmlinux.o: in function `do_arpt_get_ctl':
arp_tables.c:(.text+0x183205d): undefined reference to `xt_find_table_lock'
x86_64-linux-ld: arp_tables.c:(.text+0x18320c1): undefined reference to `xt_table_unlock'
x86_64-linux-ld: arp_tables.c:(.text+0x183219a): undefined reference to `xt_recseq'

Change these to depend on both NETFILTER_XTABLES and
NETFILTER_XTABLES_LEGACY.

Fixes: 9fce6658 ("netfilter: Exclude LEGACY TABLES on PREEMPT_RT.")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Florian Westphal <fw@strlen.de>
Tested-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>