docbook: fix v4l fatal filename error

docproc: /var/linsrc/lin2627-rc2/drivers/media/video/videodev.c: No such file or directory
make[1]: *** [Documentation/DocBook/videobook.xml] Error 1

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
cc: mchehab@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>