Tegra186: setup: Fix MISRA Rule 8.4 violation

MISRA Rule 8.4, A compatible declaration shall be visible when an
object or function with external linkage is defined.

This patch adds static for local array to fix this defect.

Change-Id: I8231448bf1bc0b1e59611d7645ca983b83d5c8e3
Signed-off-by: Anthony Zhou <anzhou@nvidia.com>

plat/nvidia/tegra/soc/t186/plat_setup.c

@@ -40,7 +40,7 @@
  * the number of power domains at the highest power level.
  *******************************************************************************
  */
-const uint8_t tegra_power_domain_tree_desc[] = {
+static const uint8_t tegra_power_domain_tree_desc[] = {
 	/* No of root nodes */
 	1,
 	/* No of clusters */