netfilter: flowtable: populate addr_type mask

nf_flow_rule_match() sets control.addr_type in key, so needs to also set
 the corresponding mask.  An exact match is wanted, so mask is all ones.

Fixes: c29f74e0 ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>