media: vivid: s_fbuf: add more sanity checks

VIDIOC_S_FBUF is by definition a scary ioctl, which is why only root
can use it. But at least check if the framebuffer parameters match that
of one of the framebuffer created by vivid, and reject anything else.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: ef834f78 ([media] vivid: add the video capture and output parts)
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>