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/pixis.c b/board/freescale/common/pixis.c
index 45dcf4d..00eb4a0 100644
--- a/board/freescale/common/pixis.c
+++ b/board/freescale/common/pixis.c
@@ -25,9 +25,8 @@
 #include <common.h>
 #include <command.h>
 #include <watchdog.h>
-
-#ifdef CONFIG_FSL_PIXIS
 #include <asm/cache.h>
+
 #include "pixis.h"
 
 
@@ -474,4 +473,3 @@
 	"    pixis_reset altbank cf <SYSCLK freq> <COREPLL ratio> <MPXPLL ratio>\n"
 	"    pixis_reset cf <SYSCLK freq> <COREPLL ratio> <MPXPLL ratio>\n"
 	);
-#endif /* CONFIG_FSL_PIXIS */