coccinelle: simple_return: Add a blank line

Insert a blank line in order to improve the readability of the
generated patch and also make it consistent with the other
.cocci files.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Michal Marek <mmarek@suse.cz>