media: atomisp: ov2680: Drop unused res member from struct ov2680_device

The res member of struct ov2680_device isn't read anywhere anymore,
drop it.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>