feat(stm32mp2-fdts): add stm32mp257f-ev1 board

Add STM32MP257F Evaluation board support. It embeds a STM32MP257FAI
SoC, with 4GB of DDR4, TSN switch (2+1 ports), 2*USB typeA, 1*USB2
typeC, SNOR OctoSPI, mini PCIe, STPMIC2 for power distribution ...

Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I92da3a7085a4d2f2d606777c4215aed55f77c589
diff --git a/fdts/stm32mp25-bl2.dtsi b/fdts/stm32mp25-bl2.dtsi
new file mode 100644
index 0000000..7a6bbbe
--- /dev/null
+++ b/fdts/stm32mp25-bl2.dtsi
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-3-Clause)
+/*
+ * Copyright (C) 2023, STMicroelectronics - All Rights Reserved
+ */
+
+/omit-if-no-ref/ &usart2_pins_a;