media: cadence: csi2rx: Implement get_fwnode_pad op

Use v4l2_subdev_get_fwnode_pad_1_to_1() as the get_fwnode_pad operation.
Cadence CSI2RX maps port numbers and pad indices 1:1.

Reviewed-by: Changhuang Liang <changhuang.liang@starfivetech.com>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Tested-by: Yemike Abhilash Chandra <y-abhilashchandra@ti.com> (on SK-AM68)
Signed-off-by: Jai Luthra <jai.luthra@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>