[media] v4l2-ctls: don't document v4l2_ctrl_fill()

This is an obsolete function that has several missing
arguments:
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'id'
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'name'
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'type'
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'min'
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'max'
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'step'
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'def'
	Warning(.//include/media/v4l2-ctrls.h:340): No description found for parameter 'flags'

However, this is an obsolete function that should be
removed soon. And are not meant to be used anymore. So,
instead of documenting those stuff, let's just make
DocBook to not handle it, by replacing "/**" by "/*".

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