media: i2c: imx258: Set pixel_rate range to the same as the value

media: i2c: imx258: Set pixel_rate range to the same as the value

With a read only control there is limited point in advertising
a minimum and maximum for the control, so change to set the
value, min, and max all to the selected pixel rate.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Luis Garcia <git@luigi311.com>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>