feat(fdts): add STM32MP1 fw-config DT files

Create all boards fw-config DT files. They all include a generic
stm32mp15-fw-config.dtsi.

Change-Id: Ib9ac8a59e93e01365001b0d11fee41f7c507c08e
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
diff --git a/fdts/stm32mp157d-dk1-fw-config.dts b/fdts/stm32mp157d-dk1-fw-config.dts
new file mode 100644
index 0000000..83116d1
--- /dev/null
+++ b/fdts/stm32mp157d-dk1-fw-config.dts
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
+/*
+ * Copyright (c) 2020-2021, STMicroelectronics - All Rights Reserved
+ */
+
+#define DDR_SIZE	0x20000000 /* 512MB */
+#include "stm32mp15-fw-config.dtsi"