sched: core_ctl: Fix possible uninitialized variable

While setting boost to cluster_data, we iterate clusters with local
uninitialized cluster variable, it is possible that, the cluster
could be null and is used in trace point.

Fix it by moving trace print to cluster validated point.

Change-Id: I466a92f2640cd5058f79355ee0cf354c41c79f7b
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>