cpuidle: lpm-levels: Optimize CPU default LPM mode for PSCI

get_cluster_id() returns the power state id which HLOS passes
to PSCI framework to do LPM modes. This function is not needed
to call for default CPU LPM modes. Do not call get_cluster_id()
for default LPM modes.

Change-Id: Ic89b0a9c031e6cecf02ec713783050d079432ae2
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>