[media] drivers/media/dvb/siano/smscoreapi.c: use list_for_each_entry

Use list_for_each_entry and perform some other induced simplifications.

The semantic match that finds the opportunity for this reorganization is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
struct list_head *pos;
struct list_head *head;
statement S;
@@

*for (pos = (head)->next; pos != (head); pos = pos->next)
S
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>