[media] V4L: Add v4l2_ctrl_subdev_log_status() helper function

This patch adds a v4l2 core helper function that can be used as
the log_status handler for subdevs that only need to log state
of the v4l2 controls owned by the subdev's control handler.

Signed-off-by: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>