netfilter: fix ebtables dependencies

Ingo Molnar reported a build error with ebtables:

ERROR: "ebt_register_table" [net/bridge/netfilter/ebtable_filter.ko] undefined!
ERROR: "ebt_do_table" [net/bridge/netfilter/ebtable_filter.ko] undefined!
ERROR: "ebt_unregister_table" [net/bridge/netfilter/ebtable_filter.ko] undefined!
ERROR: "ebt_register_table" [net/bridge/netfilter/ebtable_broute.ko] undefined!
ERROR: "ebt_do_table" [net/bridge/netfilter/ebtable_broute.ko] undefined!
ERROR: "ebt_unregister_table" [net/bridge/netfilter/ebtable_broute.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

This reason is a missing dependencies that got lost during Kconfig cleanups.
Restore it.

Tested-by: Ingo Molnar <mingo@elte.hu>

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>