cpuidle: qcom-spm: drop unnecessary initialisations

Drop the unnecessary initialisations of the platform device and driver
data pointers which are assigned on first use when registering the
cpuidle device during probe.

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>