FSL: Convert board/freescale/common/Makefile to use CONFIG_

Convert the board/freescale/common/Makefile to use
CONFIG_* options to select which files to conditionally
compile into the board/freescale/common library rather
than conditionally compiling entire files.

Now handles::
    CONFIG_FSL_PIXIS
    CONFIG_FSL_DIU_FB
    CONFIG_PQ_MDS_PIB

CONFIG_ID_EEPROM is introduced until CFG_ID_EEPROM is gone.

Signed-off-by: Jon Loeliger <jdl@freescale.com>
diff --git a/board/freescale/common/Makefile b/board/freescale/common/Makefile
index 9cee9f1..6665e7f 100644
--- a/board/freescale/common/Makefile
+++ b/board/freescale/common/Makefile
@@ -29,14 +29,13 @@
 
 LIB	= $(obj)lib$(VENDOR).a
 
-COBJS	:= sys_eeprom.o	\
-	   pixis.o	\
-	   pq-mds-pib.o \
-	   fsl_logo_bmp.o \
-	   fsl_diu_fb.o
+COBJS-${CONFIG_PQ_MDS_PIB}	+= pq-mds-pib.o
+COBJS-${CONFIG_ID_EEPROM}	+= sys_eeprom.o
+COBJS-${CONFIG_FSL_DIU_FB}	+= fsl_diu_fb.o fsl_logo_bmp.o
+COBJS-${CONFIG_FSL_PIXIS}	+= pixis.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)