AT91SAM9260EK: Move CONFIG_CMD_NAND to Makefile

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/board/atmel/at91sam9260ek/Makefile b/board/atmel/at91sam9260ek/Makefile
index 309ea46..8a629b9 100644
--- a/board/atmel/at91sam9260ek/Makefile
+++ b/board/atmel/at91sam9260ek/Makefile
@@ -25,10 +25,12 @@
 
 LIB	= $(obj)lib$(BOARD).a
 
-COBJS	:= at91sam9260ek.o led.o nand.o
+COBJS-y	+= at91sam9260ek.o
+COBJS-y	+= led.o
+COBJS-$(CONFIG_CMD_NAND) += nand.o
 
-SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS))
+SRCS	:= $(SOBJS:.o=.S) $(COBJS-y:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS-y))
 SOBJS	:= $(addprefix $(obj),$(SOBJS))
 
 $(LIB):	$(obj).depend $(OBJS) $(SOBJS)