nft-bridge: fix inversion of builtin matches

This patch fixes inversion of builtin matches by updating the use of add_*()
functions and using nft_invflags2cmp() as well.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>