[media] v4l2_subdev: describe ioctl parms at v4l2_subdev_video_ops

Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'g_std'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 's_std'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'querystd'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'cropcap'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'g_crop'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 's_crop'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'g_parm'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 's_parm'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'g_frame_interval'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 's_frame_interval'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 's_dv_timings'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'g_dv_timings'
Warning(.//include/media/v4l2-subdev.h:381): No description found for parameter 'query_dv_timings'

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