boards: arm: efm32gg_slwstk6121a: Convert to v2

Converts the board to hwmv2

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

boards/silabs/efm32gg_slwstk6121a/Kconfig.defconfig

@@ -6,10 +6,6 @@
 
 if BOARD_EFM32GG_SLWSTK6121A
 
-config BOARD
-	string
-	default "efm32gg_slwstk6121a"
-
 config CMU_HFXO_FREQ
 	default 50000000
 

boards/silabs/efm32gg_slwstk6121a/Kconfig.efm32gg_slwstk6121a

@@ -5,6 +5,4 @@
 # SPDX-License-Identifier: Apache-2.0
 
 config BOARD_EFM32GG_SLWSTK6121A
-	bool "SiLabs EFM32GG-SLWSTK6121A (WGM160P)"
-	depends on SOC_SERIES_EFM32GG11B
 	select SOC_PART_NUMBER_EFM32GG11B820F2048GM64

boards/silabs/efm32gg_slwstk6121a/board.yml

@@ -0,0 +1,5 @@
+board:
+  name: efm32gg_slwstk6121a
+  vendor: silabs
+  socs:
+  - name: efm32gg11b820f2048gm64

boards/silabs/efm32gg_slwstk6121a/efm32gg_slwstk6121a_defconfig

@@ -3,8 +3,6 @@
 # Copyright (c) 2020 Thorvald Natvig
 # SPDX-License-Identifier: Apache-2.0
 
-CONFIG_SOC_SERIES_EFM32GG11B=y
-CONFIG_BOARD_EFM32GG_SLWSTK6121A=y
 CONFIG_ARM_MPU=y
 CONFIG_CONSOLE=y
 CONFIG_UART_CONSOLE=y