boards: Convert nucleo_g431rb to HWM v2

Port the board to HWMv2.

Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>

boards/st/nucleo_g431rb/Kconfig.defconfig

@@ -5,9 +5,6 @@
 
 if BOARD_NUCLEO_G431RB
 
-config BOARD
-	default "nucleo_g431rb"
-
 config SPI_STM32_INTERRUPT
 	default y
 	depends on SPI

boards/st/nucleo_g431rb/Kconfig.nucleo_g431rb

@@ -1,8 +1,5 @@
-# STM32G431RB Nucleo board configuration
-
 # Copyright (c) 2019 Richard Osterloh <richard.osterloh@gmail.com>
 # SPDX-License-Identifier: Apache-2.0
 
 config BOARD_NUCLEO_G431RB
-	bool "Nucleo G431RB Development Board"
-	depends on SOC_STM32G431XX
+	select SOC_STM32G431XX

boards/st/nucleo_g431rb/board.yml

@@ -0,0 +1,5 @@
+board:
+  name: nucleo_g431rb
+  vendor: st
+  socs:
+    - name: stm32g431xx

boards/st/nucleo_g431rb/nucleo_g431rb_defconfig

@@ -1,8 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
 
-CONFIG_SOC_SERIES_STM32G4X=y
-CONFIG_SOC_STM32G431XX=y
-
 # enable uart driver
 CONFIG_SERIAL=y