boards: Convert nucleo_f031k6 to HWM v2

Port the board to HWMv2.

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>

boards/arm/nucleo_f031k6/Kconfig.board

@@ -1,8 +0,0 @@
-# STM32 Nucleo-32 development board with STM32F031K6 MCU configuration
-
-# Copyright (c) 2021 Sebastian Schwabe <sebastian.schwabe@mailbox.tu-dresden.de>
-# SPDX -License-Identifier: Apache-2.0
-
-config BOARD_NUCLEO_F031K6
-	bool "NUCLEO-32 F031K6 Development Board"
-	depends on SOC_STM32F031X6

boards/arm/nucleo_f031k6/Kconfig.defconfig

@@ -1,11 +0,0 @@
-# STM32 Nucleo-32 development board with STM32F031K6 MCU
-
-# Copyright (c) 2021 Sebastian Schwabe <sebastian.schwabe@mailbox.tu-dresden.de>
-# SPDX-License-Identifier: Apache-2.0
-
-if BOARD_NUCLEO_F031K6
-
-config BOARD
-	default "nucleo_f031k6"
-
-endif # BOARD_NUCLEO_F031K6

boards/v2/st/nucleo_f031k6/Kconfig.nucleo_f031k6

@@ -0,0 +1,5 @@
+# Copyright (c) 2021 Sebastian Schwabe <sebastian.schwabe@mailbox.tu-dresden.de>
+# SPDX-License-Identifier: Apache-2.0
+
+config BOARD_NUCLEO_F031K6
+	select SOC_STM32F031X6

boards/v2/st/nucleo_f031k6/board.yml

@@ -0,0 +1,5 @@
+board:
+  name: nucleo_f031k6
+  vendor: st
+  socs:
+    - name: stm32f031x6

boards/v2/st/nucleo_f031k6/nucleo_f031k6_defconfig

@@ -1,9 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 
 # Platform Configuration
-CONFIG_SOC_SERIES_STM32F0X=y
-CONFIG_SOC_STM32F031X6=y
-
 # Kernel Options due to Low Memory (4k)
 CONFIG_MAIN_STACK_SIZE=512
 CONFIG_IDLE_STACK_SIZE=150