fix(cc): code coverage optimization fix

Resolve issue where optimization is enabled for TF-A using
-Og and compile fail is seen in PSCI module.

Change-Id: Id9afb5c56a6937e7040b20cd01080c190c8276d5
Signed-off-by: Mark Dykes <mark.dykes@arm.com>
diff --git a/lib/psci/psci_common.c b/lib/psci/psci_common.c
index 41c7919..bd7a452 100644
--- a/lib/psci/psci_common.c
+++ b/lib/psci/psci_common.c
@@ -172,7 +172,8 @@
  ******************************************************************************/
 static bool psci_is_last_cpu_to_idle_at_pwrlvl(unsigned int end_pwrlvl)
 {
-	unsigned int my_idx, lvl, parent_idx;
+	unsigned int my_idx, lvl;
+	unsigned int parent_idx = 0;
 	unsigned int cpu_start_idx, ncpus, cpu_idx;
 	plat_local_state_t local_state;