V4L/DVB (6315): pvrusb2: Change list_for_each+list_entry to list_for_each_entry

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Reviewed-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>