powerpc: Enable device tree support for T1024RDB

Add device tree for T1024RDB board and enable CONFIG_OF_CONTROL
so that device tree can be compiled.
Update board README for device tree usage.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/configs/T1024RDB_NAND_defconfig b/configs/T1024RDB_NAND_defconfig
index dec0044..27ed0e7 100644
--- a/configs/T1024RDB_NAND_defconfig
+++ b/configs/T1024RDB_NAND_defconfig
@@ -45,6 +45,8 @@
 CONFIG_CMD_FAT=y
 CONFIG_MTDIDS_DEFAULT="nor0=fe8000000.nor,nand0=fff800000.flash,spi0=spife110000.1"
 CONFIG_MTDPARTS_DEFAULT="mtdparts=fe8000000.nor:1m(uboot),5m(kernel),128k(dtb),96m(fs),-(user);fff800000.flash:1m(uboot),5m(kernel),128k(dtb),96m(fs),-(user);spife110000.0:1m(uboot),5m(kernel),128k(dtb),-(user)"
+CONFIG_OF_CONTROL=y
+CONFIG_DEFAULT_DEVICE_TREE="t1024rdb"
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_FSL_CAAM=y
 CONFIG_SYS_FSL_DDR3=y
@@ -70,4 +72,3 @@
 CONFIG_FSL_ESPI=y
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y
-CONFIG_OF_LIBFDT=y