stm32mp1: enable PIE for BL32

In order to prepare future support of FIP, BL32 (SP_min) is compiled
as Position Independent Executable.

Change-Id: I15e7cc433fb03e1833002f4fe2eaecb6ed42eb47
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
diff --git a/plat/st/stm32mp1/platform.mk b/plat/st/stm32mp1/platform.mk
index 3595819..50fb1b7 100644
--- a/plat/st/stm32mp1/platform.mk
+++ b/plat/st/stm32mp1/platform.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2021, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -9,6 +9,8 @@
 BL2_AT_EL3		:=	1
 USE_COHERENT_MEM	:=	0
 
+ENABLE_PIE		:=	1
+
 STM32_TF_VERSION	?=	0
 
 # Enable dynamic memory mapping