cpuidle: qcom-spm: fix device and OF node leaks at probe

Make sure to drop the reference to the saw device taken by
of_find_device_by_node() after retrieving its driver data during
probe().

Also drop the reference to the CPU node sooner to avoid leaking it in
case there is no saw node or device.

Fixes: 60f3692b ("cpuidle: qcom_spm: Detach state machine from main SPM handling")
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>