cpuidle: lpm-levels-legacy: Use of_node_put on node pointers

Add missing of_node_put calls on node pointers to decrement
ref counts for legacy lpm.

Change-Id: I42440c57b7a56337a9ca9534c34cdf02fba2e570
Signed-off-by: Chinkit Kumar,Kirti Kumar Parmar <parma@codeaurora.org>