media: ov2680: Fix exposure and gain ctrls range and default value

The exposure control's max effective value is VTS - 8, set the control
range to match this. Thas means that if/when a future commit makes VTS
configurable as a control itself the exposure range needs to be
updated dynamically to match the VTS value.

The gain control goes from 0 - 1023, higher values wrap around to
the lowest gain setting.

The gain control, controls an analog gain so use V4L2_CID_ANALOGUE_GAIN
for it instead of V4L2_CID_GAIN.

Also stop setting 0 as default for both controls this leads to
a totally black picture which is no good. This is esp. important
for tests of the sensor driver without (userspace driven)
auto exposure / gain.

Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>