media: sun6i-csi: Tidy up Kconfig

Update the option title and help, group related options together,
add dependency on VIDEO_DEV since the driver uses it and update the
description.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>