[media] diff-v4l.rst: Fix V4L version 1 references

The V4L version 1 structures had long gone from the Linux Kernel.
It doesn't make sense to use cross-references for them, as they
won't be found.

So, get rid of them.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>