media: ov5640: set correct default link frequency

current_link_freq field in ov5640_dev structure is link frequency,
not link frequency array index, so correct it.

Fixes: 3c28588f ("media: ov5640: Update pixel_rate and link_freq")
Signed-off-by: Guoniu.zhou <guoniu.zhou@nxp.com>
Acked-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>