nds32: Support relocation.

Enable pie option for relocation.

Signed-off-by: rick <rick@andestech.com>
Cc: Andes <uboot@andestech.com>
diff --git a/arch/nds32/config.mk b/arch/nds32/config.mk
index 5ac9f90..ca76641 100644
--- a/arch/nds32/config.mk
+++ b/arch/nds32/config.mk
@@ -19,4 +19,4 @@
 PLATFORM_RELFLAGS	+= -gdwarf-2
 PLATFORM_CPPFLAGS	+= -D__nds32__ -G0 -ffixed-10 -fpie
 
-LDFLAGS_u-boot		= --gc-sections --relax
+LDFLAGS_u-boot		= --gc-sections --relax -pie