nds32: Convert Makefiles to use COBJS-y style

Signed-off-by: Kuan-Yu Kuo <ken.kuoky@gmail.com>
Cc: Macpaul Lin <macpaul@gmail.com>
diff --git a/board/AndesTech/adp-ag101/Makefile b/board/AndesTech/adp-ag101/Makefile
index d55a799..867e1cf 100644
--- a/board/AndesTech/adp-ag101/Makefile
+++ b/board/AndesTech/adp-ag101/Makefile
@@ -26,10 +26,10 @@
 
 LIB	= $(obj)lib$(BOARD).o
 
-COBJS	:= adp-ag101.o
+COBJS-y	:= adp-ag101.o
 
-SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS) $(SOBJS))
+SRCS	:= $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS-y) $(SOBJS-y))
 
 $(LIB):	$(OBJS)
 	$(call cmd_link_o_target, $(OBJS))