boards: Convert stm32h735g_disco to HWM v2

Port the board to HWMv2.

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

boards/st/stm32h735g_disco/Kconfig.defconfig

@@ -5,9 +5,6 @@
 
 if BOARD_STM32H735G_DISCO
 
-config BOARD
-	default "stm32h735g_disco"
-
 if NETWORKING
 
 config NET_L2_ETHERNET

boards/st/stm32h735g_disco/Kconfig.stm32h735g_disco

@@ -1,8 +1,5 @@
-# STM32H735G Discovery board configuration
-
 # Copyright (c) 2021 SILA Embedded Solutions GmbH
 # SPDX-License-Identifier: Apache-2.0
 
 config BOARD_STM32H735G_DISCO
-	bool "STM32H735G Discovery Development Board"
-	depends on SOC_STM32H735XX
+	select SOC_STM32H735XX

boards/st/stm32h735g_disco/board.yml

@@ -0,0 +1,5 @@
+board:
+  name: stm32h735g_disco
+  vendor: st
+  socs:
+    - name: stm32h735xx

boards/st/stm32h735g_disco/doc/index.rst

@@ -77,8 +77,8 @@ The current Zephyr stm32h735g_disco board configuration supports the following h
 
 Other hardware features are not yet supported on Zephyr porting.
 
-The default configuration per core can be found in the defconfig file:
-``boards/arm/stm32h735g_disco/stm32h735g_disco_defconfig``
+The default configuration can be found in the defconfig file:
+:zephyr_file:`boards/st/stm32h735g_disco/stm32h735g_disco_defconfig`
 
 Pin Mapping
 ===========

boards/st/stm32h735g_disco/stm32h735g_disco_defconfig

@@ -1,8 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
 
-CONFIG_SOC_SERIES_STM32H7X=y
-CONFIG_SOC_STM32H735XX=y
-
 # Enable the internal SMPS regulator
 CONFIG_POWER_SUPPLY_DIRECT_SMPS=y