media: ov2680: Add ov2680_fill_format() helper function

Add a ov2680_fill_format() helper function and use this everywhere were
a v4l2_mbus_framefmt struct needs to be filled in so that the driver always
fills it consistently.

This is a preparation patch for fixing ov2680_set_fmt()
which == V4L2_SUBDEV_FORMAT_TRY calls not properly filling in
the passed in v4l2_mbus_framefmt struct.

Note that for ov2680_init_cfg() this now simply always fills
the try_fmt struct of the passed in sd_state. This is correct because
ov2680_init_cfg() is never called with a NULL sd_state so the old
sd_state check is not necessary.

Fixes: 3ee47cad ("media: ov2680: Add Omnivision OV2680 sensor driver")
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>