[media] smiapp: Make clock control optional

The clock control is not explicitly controlled by the driver in two cases:
ACPI based systems and when the clock is part of the power sequence of the
camera module.

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