netfilter: ecache: remove one indent level

nf_conntrack_eventmask_report and nf_ct_deliver_cached_events shared
most of their code.  This unifies the layout by changing

 if (nf_ct_is_confirmed(ct)) {
   foo
 }

 to
 if (!nf_ct_is_confirmed(ct)))
   return
 foo

This removes one level of indentation.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>