netfilter: nft_reject_bridge: fix build errors due to code movement

Fix build errors in net/bridge/netfilter/nft_reject_bridge.ko
by selecting NF_REJECT_IPV4, which provides the missing symbols.

ERROR: modpost: "nf_reject_skb_v4_tcp_reset" [net/bridge/netfilter/nft_reject_bridge.ko] undefined!
ERROR: modpost: "nf_reject_skb_v4_unreach" [net/bridge/netfilter/nft_reject_bridge.ko] undefined!

Fixes: fa538f7c ("netfilter: nf_reject: add reject skbuff creation helpers")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>