netfilter: nf_tables: hook list memleak in flowtable deletion

After looking up for the flowtable hooks that need to be removed,
release the hook objects in the deletion list. The error path needs to
released these hook objects too.

Fixes: abadb2f8 ("netfilter: nf_tables: delete devices from flowtable")
Reported-by:  <syzbot+eb9d5924c51d6d59e094@syzkaller.appspotmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>