media: Documentation: Deprecate s_stream video op, update docs

The scope of the s_stream video operation is now fully supported by
{enable,disable}_streams. Explicitly document the s_stream() op as
deprecated and update the related documentation.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>