board: stm32f429-discovery: switch to DM STM32 sdram driver

Use available DM stm32_sdram.c driver instead of board
SDRAM initialization.
For that, enable OF_CONTROL, OF_EMBED and STM32_SDRAM flags.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/configs/stm32f429-discovery_defconfig b/configs/stm32f429-discovery_defconfig
index 9339e36..1cf3b6a 100644
--- a/configs/stm32f429-discovery_defconfig
+++ b/configs/stm32f429-discovery_defconfig
@@ -2,6 +2,7 @@
 CONFIG_STM32=y
 CONFIG_STM32F4=y
 CONFIG_TARGET_STM32F429_DISCOVERY=y
+CONFIG_DEFAULT_DEVICE_TREE="stm32f429-disco"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 earlyprintk consoleblank=0 ignore_loglevel"
@@ -14,7 +15,10 @@
 CONFIG_CMD_IMLS=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_TIMER=y
+CONFIG_OF_CONTROL=y
+CONFIG_OF_EMBED=y
 CONFIG_ENV_IS_IN_FLASH=y
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
-CONFIG_OF_LIBFDT=y
+CONFIG_RAM=y
+CONFIG_STM32_SDRAM=y