nds32: Add macro definition for offset of lp register on stack

Use macro to replace the magic number.
Signed-off-by: NZong Li <zong@andestech.com>
Acked-by: NGreentime Hu <greentime@andestech.com>
Signed-off-by: NGreentime Hu <greentime@andestech.com>

arch/nds32/include/asm/nds32.h

@@ -17,6 +17,7 @@
 #else
 #define FP_OFFSET (-2)
 #endif
+#define LP_OFFSET (-1)
 
 extern void __init early_trap_init(void);
 static inline void GIE_ENABLE(void)

arch/nds32/kernel/stacktrace.c

@@ -31,7 +31,7 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 	       && (fpn >= (unsigned long *)TASK_SIZE)) {
 		unsigned long lpp, fpp;
 
-		lpp = fpn[-1];
+		lpp = fpn[LP_OFFSET];
 		fpp = fpn[FP_OFFSET];
 		if (!__kernel_text_address(lpp))
 			break;

arch/nds32/kernel/traps.c

@@ -117,7 +117,7 @@ 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;
-			ret_addr = base_reg[-1];
+			ret_addr = base_reg[LP_OFFSET];
 			next_fp = base_reg[FP_OFFSET];
 			if (__kernel_text_address(ret_addr)) {