[media] v4l: vsp1: Add FCP support

On some platforms the VSP performs memory accesses through an FCP. When
that's the case get a reference to the FCP from the VSP DT node and
enable/disable it at runtime as needed.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>