media: v4l: fix broken video4linux docs locations

There are several places pointing to old documentation files:

  Documentation/video4linux/API.html
  Documentation/video4linux/bttv/
  Documentation/video4linux/cx2341x/fw-encoder-api.txt
  Documentation/video4linux/m5602.txt
  Documentation/video4linux/v4l2-framework.txt
  Documentation/video4linux/videobuf
  Documentation/video4linux/Zoran

Make them point to the new location where available, removing
otherwise.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Jonathan Corbet <corbet@lwn.net>