FVP: Enable PIE for RESET_TO_BL31=1

This patch enabled PIE for FVP when RESET_TO_BL31=1. The references
to BL31_BASE are replaced by BL31_START as being a symbol exported by
the linker, will create a dynamic relocation entry in .rela.dyn and
hence will be fixed up by dynamic linker at runtime. Also, we disable
RECLAIM_INIT_CODE when PIE is enabled as the init section overlay
creates some static relocations which cannot be handled by the
dynamic linker currently.

Change-Id: I86df1b0a8b2a8bbbe7c3f3c0b9a08c86c2963ec0
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
diff --git a/plat/arm/board/fvp/platform.mk b/plat/arm/board/fvp/platform.mk
index 332df4d..3d858c2 100644
--- a/plat/arm/board/fvp/platform.mk
+++ b/plat/arm/board/fvp/platform.mk
@@ -202,7 +202,9 @@
 DYNAMIC_WORKAROUND_CVE_2018_3639	:=	1
 
 # Enable reclaiming of BL31 initialisation code for secondary cores stacks for FVP
+ifneq (${RESET_TO_BL31},1)
 RECLAIM_INIT_CODE	:=	1
+endif
 
 ifeq (${ENABLE_AMU},1)
 BL31_SOURCES		+=	lib/cpus/aarch64/cortex_a75_pubsub.c	\