media: atomisp: Rename camera to sensor

The camera v4l2_subdev pointer in struct atomisp_input_subdev points to
an image sensor, rename camera to sensor to make this more clear.

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