Implement get_sys_suspend_power_state() handler for Tegra

This patch implements the get_sys_suspend_power_state() handler required by
the PSCI SYSTEM_SUSPEND API. The intent of this handler is to return the
appropriate State-ID field which can be utilized in `affinst_suspend()` to
suspend to system affinity level.

Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
diff --git a/plat/nvidia/tegra/include/t210/tegra_def.h b/plat/nvidia/tegra/include/t210/tegra_def.h
index c72d081..a54de5a 100644
--- a/plat/nvidia/tegra/include/t210/tegra_def.h
+++ b/plat/nvidia/tegra/include/t210/tegra_def.h
@@ -34,6 +34,20 @@
 #include <platform_def.h>
 
 /*******************************************************************************
+ * Power down state IDs
+ ******************************************************************************/
+#define PSTATE_ID_CORE_POWERDN		7
+#define PSTATE_ID_CLUSTER_IDLE		16
+#define PSTATE_ID_CLUSTER_POWERDN	17
+#define PSTATE_ID_SOC_POWERDN		27
+
+/*******************************************************************************
+ * This value is used by the PSCI implementation during the `SYSTEM_SUSPEND`
+ * call as the `state-id` field in the 'power state' parameter.
+ ******************************************************************************/
+#define PLAT_SYS_SUSPEND_STATE_ID	PSTATE_ID_SOC_POWERDN
+
+/*******************************************************************************
  * Implementation defined ACTLR_EL3 bit definitions
  ******************************************************************************/
 #define ACTLR_EL3_L2ACTLR_BIT		(1 << 6)