nds32: Fix boot fail issue when build with elf-mculib.

Add -mcmodel=large can let elf-mculib have
the same default behavior just like linux-glibc.
And it help to pass U-Boot booting sequence.

Signed-off-by: Rick Chen <rick@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
diff --git a/arch/nds32/config.mk b/arch/nds32/config.mk
index 4e10de0..a1c3371 100644
--- a/arch/nds32/config.mk
+++ b/arch/nds32/config.mk
@@ -17,6 +17,6 @@
 
 PLATFORM_RELFLAGS	+= -fno-common -mrelax -mno-ext-fpu-dp -mfloat-abi=soft
 PLATFORM_RELFLAGS	+= -gdwarf-2
-PLATFORM_CPPFLAGS	+= -D__nds32__ -ffixed-10 -fpie
+PLATFORM_CPPFLAGS	+= -D__nds32__ -ffixed-10 -fpie -mcmodel=large
 
 LDFLAGS_u-boot		= --gc-sections --relax -pie --mabi=AABI