[media] v4l: vsp1: Remove support for platform data

Now that all platforms instantiate the VSP1 through DT, platform data
support isn't needed anymore.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>