media: i2c: imx219: Simplify code handling in s_fmt

The imx219_set_pad_format() function adjusts the media bus code provided
through the v4l2_subdev_format parameter to a media bus code known
to be supported by the sensor.

The same exact operation is performed by the imx219_get_format_code()
function which called by imx219_update_pad_format(), which is in the
imx219_set_pad_format() call path.

Remove the duplicated operation and simplify imx219_set_pad_format().

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>