media: smiapp: Use pm_runtime_get_if_active

Use the convenience function pm_runtime_get_if_active() instead of a
number of calls to runtime PM to figure out if the device was already
powered up.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>