[media] sh_mobile_ceu_camera: Do not call vb2's mem_ops directly

Use vb2_dma_contig_plane_paddr to retrieve a physical address for a plane
instead of calling an internal mem_ops callback.

Signed-off-by: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>