media: pxa_camera: Drop usage of .set_mbus_config()

The subdev .set_mbus_config() operation is deprecated and will be
dropped. Drop its usage from the pxa_camera driver, querying the sensor
bus configuration instead of setting it. Only the ov6650 driver supports
the operation, any platform that experiences issues with this change
should update the ov6650 configuration to match what pxa_camera
supports.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>