media: saa7134: convert list_for_each to entry variant

Convert list_for_each() to list_for_each_entry() where
applicable.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>