[media] smiapp: Fully probe the device in probe

In the case of platform data, ISPs that provide clocks to the sensor must
probe before the sensor does. Accessing the sensor does require the clocks,
and thus, probe cannot access the sensor in such a system.

This limitation does not exist in the case of the DT. Perform all
initialisation except Media entity initialisation, link creation and
sub-device registration in probe.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>