arm: socfpga: mailbox: Add 'SYSTEM_RESET' PSCI support to mbox_reset_cold()

mbox_reset_cold() will invoke ATF's PSCI service when running in
non-secure mode (EL2).

Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>
diff --git a/arch/arm/mach-socfpga/mailbox_s10.c b/arch/arm/mach-socfpga/mailbox_s10.c
index 18d4492..429444f 100644
--- a/arch/arm/mach-socfpga/mailbox_s10.c
+++ b/arch/arm/mach-socfpga/mailbox_s10.c
@@ -11,6 +11,7 @@
 #include <asm/arch/mailbox_s10.h>
 #include <asm/arch/system_manager.h>
 #include <asm/secure.h>
+#include <asm/system.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -398,6 +399,9 @@
 
 int mbox_reset_cold(void)
 {
+#if !defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_ATF)
+	psci_system_reset();
+#else
 	int ret;
 
 	ret = mbox_send_cmd(MBOX_ID_UBOOT, MBOX_REBOOT_HPS, MBOX_CMD_DIRECT,
@@ -406,6 +410,7 @@
 		/* mailbox sent failure, wait for watchdog to kick in */
 		hang();
 	}
+#endif
 	return 0;
 }