[media] media: rcar_vin: fill in bus_info field

Adapt rcar_vin_querycap() so that cap->bus_info is populated with
something meaningful/unique.

Signed-off-by: Rob Taylor <rob.taylor@codethink.co.uk>
Signed-off-by: William Towle <william.towle@codethink.co.uk>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>