powerpc: Enable device tree support for P2041RDB

Add device tree for P1041RDB 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/P2041RDB_SDCARD_defconfig b/configs/P2041RDB_SDCARD_defconfig
index c339f1b..1816aa8 100644
--- a/configs/P2041RDB_SDCARD_defconfig
+++ b/configs/P2041RDB_SDCARD_defconfig
@@ -2,6 +2,7 @@
 CONFIG_SYS_TEXT_BASE=0xFFF40000
 CONFIG_MPC85xx=y
 CONFIG_TARGET_P2041RDB=y
+CONFIG_MPC85XX_HAVE_RESET_VECTOR=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
@@ -23,6 +24,8 @@
 CONFIG_MP=y
 CONFIG_CMD_EXT2=y
 CONFIG_CMD_FAT=y
+CONFIG_OF_CONTROL=y
+CONFIG_DEFAULT_DEVICE_TREE="p2041rdb"
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_FSL_CAAM=y
 CONFIG_FSL_ESDHC=y
@@ -45,4 +48,3 @@
 CONFIG_FSL_ESPI=y
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y
-CONFIG_OF_LIBFDT=y