media: rkisp1: capture: Initialize entity before video device

The media_entity embedded in the video_device needs to be initialized
before registering the video_device. Do so.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Dafna Hirschfeld <dafna@fastmail.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>