Tegra186: implement prepare_system_reset handler

This patch implements the 'prepare_system_reset' handler to
issue the 'system reset' command to the MCE.

Change-Id: I83d8d0b4167aac5963d640fe77d5754dc7ef05b1
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

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

@@ -114,3 +114,10 @@ __dead2 void tegra_soc_prepare_system_off(void)
 {
 	mce_enter_ccplex_state(TEGRA_ARI_MISC_CCPLEX_SHUTDOWN_POWER_OFF);
 }
+
+int tegra_soc_prepare_system_reset(void)
+{
+	mce_enter_ccplex_state(TEGRA_ARI_MISC_CCPLEX_SHUTDOWN_REBOOT);
+
+	return PSCI_E_SUCCESS;
+}