[media] smiapp: Always initialise the sensor in probe

Initialise the sensor in probe. The reason why it wasn't previously done
in case of platform data was that the probe() of the driver that provided
the clock through the set_xclk() callback would need to finish before the
probe() function of the smiapp driver. The set_xclk() callback no longer
exists.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>