V4L/DVB (8549a): fix kernel-doc warning, function name, and docbook filename

Change function name in kernel-doc and add kernel-doc for parameter @index:
Warning(linhead//drivers/media/video/videodev.c:2090): No description found for parameter 'index'

Also change source file name in DocBook/videobook.tmpl to match the new
source file name.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>