media: i2c: adv748x: csi2: set entity function to video interface bridge

The ADV748x CSI-2 subdevices are HDMI/AFE to MIPI CSI-2 bridges.

Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Acked-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>