powerpc/t4rdb: Add SD boot support for T4240RDB board

This patch adds SD boot support for T4240RDB board. SPL
framework is used. PBL initializes the internal RAM and
copies SPL to it. Then SPL initializes DDR using SPD and
copies u-boot from SD card to DDR, finally SPL transfers
control to u-boot.

Signed-off-by: Chunhe Lan <Chunhe.Lan@freescale.com>
[York Sun: Fix T4240RDB_SDCARD_defcofig]
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/board/freescale/t4rdb/t4_rcw.cfg b/board/freescale/t4rdb/t4_rcw.cfg
index e46c7b2..282fea48 100644
--- a/board/freescale/t4rdb/t4_rcw.cfg
+++ b/board/freescale/t4rdb/t4_rcw.cfg
@@ -2,6 +2,6 @@
 aa55aa55 010e0100
 #serdes protocol  27_55_1_9
 16070019 18101916 00000000 00000000
-6c6e0848 00448c00 6c020000 f5000000
-00000000 ee0000ee 00000000 000287fc
-00000000 50000000 00000000 00000028
+6c6e0848 00448c00 ec020000 f5000000
+00000000 ee0000ee 00000000 000307fc
+00000000 00000000 00000000 00000028