media: amlogic: c3-mipi-csi2: Call v4l2_get_link_freq() on source pad

media: amlogic: c3-mipi-csi2: Call v4l2_get_link_freq() on source pad

Call v4l2_get_link_freq() on the source pad so we can remove the
workaround that allows calling it on a control handler.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Keke Li <keke.li@amlogic.com>
Tested-by: Keke Li <keke.li@amlogic.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>