media: v4l: subdev: Make stream argument optional in state access functions

The sub-device state access functions take three arguments: sub-device
state, pad and stream. The stream is not relevant for the majority of
drivers and having to specify 0 for the stream is considered a nuisance.

Provide a two-argument macros for these state access functions to cover
the needs of stream-unaware users.

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