netfilter: constify nf_loginfo structures

The nf_loginfo structures are only passed as the seventh argument to
nf_log_trace, which is declared as const or stored in a local const
variable.  Thus the nf_loginfo structures themselves can be const.

Done with the help of Coccinelle.

// <smpl>
@r disable optional_qualifier@
identifier i;
position p;
@@
static struct nf_loginfo i@p = { ... };

@ok1@
identifier r.i;
expression list[6] es;
position p;
@@
 nf_log_trace(es,&i@p,...)

@ok2@
identifier r.i;
const struct nf_loginfo *e;
position p;
@@
 e = &i@p

@bad@
position p != {r.p,ok1.p,ok2.p};
identifier r.i;
struct nf_loginfo e;
@@
e@i@p

@depends on !bad disable optional_qualifier@
identifier r.i;
@@
static
+const
 struct nf_loginfo i = { ... };
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>