media: dw9714: Call pm_runtime_idle() at the end of probe()

Call pm_runtime_idle() at the end of the driver's probe() function to
enable the device to reach low power state once probe() finishes.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>