Fix compilation error for MCF5275

Rename OBJ to COBJ in board/platform/Makefile
Signed-off-by: NTsiChung Liew <Tsi-Chung.Liew@freescale.com>

board/freescale/m5275evb/Makefile

@@ -25,7 +25,7 @@ include $(TOPDIR)/config.mk
 
 LIB	= $(obj)lib$(BOARD).a
 
-OBJS	= $(BOARD).o mii.o
+COBJS	= $(BOARD).o mii.o
 
 SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))