intel: clear 'PLAT_SEC_ENTRY' in early platform setup

Ensure 'PLAT_SEC_ENTRY' is cleared during early platform
setup. This is to prevent the slave CPU cores jump to the stale
entry point after warm reset when using U-Boot SPL as first
stage boot loader.

Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>
Change-Id: I3294ce2f74aa691d0cf311fa30f27f9d4fb8800a
diff --git a/plat/intel/soc/stratix10/bl31_plat_setup.c b/plat/intel/soc/stratix10/bl31_plat_setup.c
index 5813c8f..e0c3054 100644
--- a/plat/intel/soc/stratix10/bl31_plat_setup.c
+++ b/plat/intel/soc/stratix10/bl31_plat_setup.c
@@ -1,6 +1,6 @@
 /*
- * Copyright (c) 2019, ARM Limited and Contributors. All rights reserved.
- * Copyright (c) 2019, Intel Corporation. All rights reserved.
+ * Copyright (c) 2019-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2019-2020, Intel Corporation. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -47,6 +47,8 @@
 {
 	static console_t console;
 
+	mmio_write_64(PLAT_SEC_ENTRY, PLAT_SEC_WARM_ENTRY);
+
 	console_16550_register(PLAT_UART0_BASE, PLAT_UART_CLOCK, PLAT_BAUDRATE,
 		&console);
 	/*