refactor(boards): Migrate s40nc to HWMv2

Move the ShortyFortyNoCordy (s40nc) to HWMv2.

app/boards/arm/s40nc/Kconfig.board

@@ -1,6 +0,0 @@
-# Copyright (c) 2021 The ZMK Contributors
-# SPDX-License-Identifier: MIT
-
-config BOARD_S40NC
-    bool "S40NC"
-    depends on SOC_NRF52840_QIAA

app/boards/mechwild/s40nc/Kconfig.s40nc

@@ -0,0 +1,8 @@
+# Copyright (c) 2021 The ZMK Contributors
+# SPDX-License-Identifier: Apache-2.0
+
+config BOARD_S40NC
+    select SOC_NRF52840_QIAA
+    imply RETAINED_MEM
+    imply RETENTION
+    imply RETENTION_BOOT_MODE

app/boards/mechwild/s40nc/board.yml

@@ -0,0 +1,5 @@
+board:
+  name: s40nc
+  vendor: mechwild
+  socs:
+    - name: nrf52840

app/boards/mechwild/s40nc/s40nc.dts

@@ -6,6 +6,8 @@
 
 /dts-v1/;
 #include <nordic/nrf52840_qiaa.dtsi>
+#include <common/nordic/nrf52840_uf2_boot_mode.dtsi>
+
 #include <dt-bindings/zmk/matrix_transform.h>
 
 / {

app/boards/mechwild/s40nc/s40nc_defconfig

@@ -1,10 +1,6 @@
 # Copyright (c) 2021 The ZMK Contributors
 # SPDX-License-Identifier: MIT
 
-CONFIG_SOC_SERIES_NRF52X=y
-CONFIG_SOC_NRF52840_QIAA=y
-CONFIG_BOARD_S40NC=y
-
 # Enable MPU
 CONFIG_ARM_MPU=y