[media] smiapp: Return -EPROBE_DEFER if the clock cannot be obtained

The clock may be provided by a driver which is yet to probe. Print the
actual error code as well.

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>