The FrameBuffer class is only friends with Request so that the request
can be associated with the buffers.
FrameBuffer already has a helper to setRequest(), so let's use that
directly instead.
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>