nds32: Fix empty call trace

The compiler predefined macro 'NDS32_ABI_2' had been removed, it should
use the '__NDS32_ABI_2' here.
Signed-off-by: Zong Li <zong@andestech.com>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

arch/nds32/kernel/traps.c

@@ -137,7 +137,7 @@ static void __dump(struct task_struct *tsk, unsigned long *base_reg)
 		       !((unsigned long)base_reg & 0x3) &&
 		       ((unsigned long)base_reg >= TASK_SIZE)) {
 			unsigned long next_fp;
-#if !defined(NDS32_ABI_2)
+#if !defined(__NDS32_ABI_2)
 			ret_addr = base_reg[0];
 			next_fp = base_reg[1];
 #else