media: i2c: imx258: Use v4l2_link_freq_to_bitmap helper

Use the v4l2_link_freq_to_bitmap() helper to figure out which
driver-supported link freq can be used on a given system.

Signed-off-by: Luis Garcia <git@luigi311.com>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Tommaso Merciai <tomm.merciai@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>