The association of buffers to a request can be done directly in
addBuffer() instead of when the request is queued to the camera. Keep
the check that a request contains buffers by moving it to
Camera::queueRequest() where prepare() was previously called.
As a bonus we can remove a friend statement in Request.
Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>