[media] media: adv7180: add adv7180cp, adv7180st compatible strings

Used to differentiate between models with 3 and 6 inputs.

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>