ARM: fix broken build of ARM

Commit 8aba9dce breaks
ARM boards because for ARM the -pie option is used
for partial linking together with -r option.

The patch adds the -pie option to link u-boot.bin only.

Signed-off-by: Stefano Babic <sbabic@denx.de>
CC: Jason Liu <liu.h.jason@gmail.com>
CC: lool@dooz.org
CC: Wolfgang Denk <wd@denx.de>
CC: Albert Aribaud <albert.aribaud@free.fr>
Tested-by: Alexander Holler <holler@ahsoftware.de>

arch/arm/config.mk

@@ -67,5 +67,5 @@ LDSCRIPT := $(SRCTREE)/$(CPUDIR)/u-boot.lds
 
 # needed for relocation
 ifndef CONFIG_NAND_SPL
-PLATFORM_LDFLAGS += -pie
+LDFLAGS_u-boot += -pie
 endif