v4l: rcar-fcp: Don't get/put module reference

Direct callers of the FCP API hold a reference to the FCP module due to
module linkage, there's no need to take another one manually. Take a
reference to the device instead to ensure that it won't disappear behind
the caller's back.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Acked-by: Mauro Cavalho Chehab <mchehab@s-opensource.com>