stm32f4: Add support for stm32f429-discovery board

Signed-off-by: Kamil Lulko <rev13@wp.pl>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/stm32f429-discovery_defconfig b/configs/stm32f429-discovery_defconfig
new file mode 100644
index 0000000..6d74d73
--- /dev/null
+++ b/configs/stm32f429-discovery_defconfig
@@ -0,0 +1,2 @@
+CONFIG_ARM=y
+CONFIG_TARGET_STM32F429_DISCOVERY=y