boards: Convert stm32mp157c_dk2 to HWM v2

Port the board to HWMv2.

Signed-off-by: Abderrahmane Jarmouni <abderrahmane.jarmouni-ext@st.com>

boards/boards_legacy/arm/stm32mp157c_dk2/Kconfig.board

@@ -1,8 +0,0 @@
-# STM32MP157C Discovery board configuration
-
-# Copyright (c) 2019 STMicroelectronics
-# SPDX-License-Identifier: Apache-2.0
-
-config BOARD_STM32MP157C_DK2
-	bool "STM32MP157C Discovery Development 2 Board"
-	depends on SOC_STM32MP15_M4

boards/st/stm32mp157c_dk2/Kconfig.defconfig

@@ -5,9 +5,6 @@
 
 if BOARD_STM32MP157C_DK2
 
-config BOARD
-	default "stm32mp157c_dk2"
-
 config SPI_STM32_INTERRUPT
 	default y
 	depends on SPI

boards/st/stm32mp157c_dk2/Kconfig.stm32mp157c_dk2

@@ -0,0 +1,5 @@
+# Copyright (c) 2019 STMicroelectronics
+# SPDX-License-Identifier: Apache-2.0
+
+config BOARD_STM32MP157C_DK2
+	select SOC_STM32MP15_M4

boards/st/stm32mp157c_dk2/board.yml

@@ -0,0 +1,5 @@
+board:
+  name: stm32mp157c_dk2
+  vendor: st
+  socs:
+    - name: stm32mp157cxx

boards/st/stm32mp157c_dk2/stm32mp157c_dk2_defconfig

@@ -1,6 +1,3 @@
-CONFIG_SOC_SERIES_STM32MP1X=y
-CONFIG_SOC_STM32MP15_M4=y
-
 # enable GPIO
 CONFIG_GPIO=y