media: subdev: add locking wrappers to subdev op wrappers

It is common that media drivers call subdev ops in source subdevs, and
pass NULL as the state. This was the way to indicate that the callee
should use the callee's private active state.

E.g.:

v4l2_subdev_call(priv->source_sd, pad, get_fmt, NULL, &sd_fmt);

Now that we have a real subdev active state in the v4l2_subdev struct,
we want the caller to pass a proper state (when available). And
furthermore, the state should be locked.

This would mean changing all the callers, which is the long term goal.

To fix this issue in the short term, let's add an extra wrapper layer to
all v4l2_subdev_call_pad_wrappers which deal with states. These wrappers
handle the state == NULL case by using the locked active state instead
(when available).

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>