[media] vimc: sen: Declare vimc_sen_video_ops as static

Declare vimc_sen_video_ops as static, remove warning from sparse tool

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>