media: smiapp: Add support for flash and lens devices

Parse async sub-devices related to the sensor by switching the async
sub-device registration function.

These types devices aren't directly related to the sensor, but are
nevertheless handled by the smiapp driver due to the relationship of these
component to the main part of the camera module --- the sensor.

This does not yet address providing the user space with information on how
to associate the sensor or lens devices but the kernel now has the
necessary information to do that.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>