refactor(boards): Move Polarity Works boards to ZMK variants

Make the standard Polarity Works board IDs be `zmk` variants.

app/boards/polarityworks/bt60/board.yml

@@ -3,10 +3,14 @@ boards:
     vendor: polarityworks
     socs:
       - name: nrf52840
+        variants:
+          - name: zmk
   - name: bt60
     vendor: polarityworks
     socs:
       - name: nrf52840
+        variants:
+          - name: zmk
     revision:
       format: major.minor.patch
       default: 2.0.0

app/boards/polarityworks/bt60/bt60.zmk.yml

@@ -1,5 +1,5 @@
 file_format: "1"
-id: bt60
+id: bt60//zmk
 name: BT60 V2
 type: board
 arch: arm

app/boards/polarityworks/bt60/bt60_hs.zmk.yml

@@ -1,5 +1,5 @@
 file_format: "1"
-id: bt60_hs
+id: bt60_hs//zmk
 name: BT60 V1 Hotswap
 type: board
 arch: arm

app/boards/polarityworks/bt60/bt60_hs_nrf52840_zmk.dts

@@ -4,7 +4,7 @@
 * SPDX-License-Identifier: MIT
 */
 
-#include "bt60.dts"
+#include "bt60_nrf52840_zmk.dts"
 #include "bt60_1_0_0.dtsi"
 #include <layouts/common/60percent/ansi.dtsi>
 

app/boards/polarityworks/bt65/board.yml

@@ -3,3 +3,5 @@ board:
   vendor: polarityworks
   socs:
     - name: nrf52840
+      variants:
+        - name: zmk

app/boards/polarityworks/bt65/bt65.zmk.yml

@@ -1,5 +1,5 @@
 file_format: "1"
-id: bt65
+id: bt65//zmk
 name: BT65
 type: board
 arch: arm

app/boards/polarityworks/bt75/board.yml

@@ -3,3 +3,5 @@ board:
   vendor: polarityworks
   socs:
     - name: nrf52840
+      variants:
+        - name: zmk

app/boards/polarityworks/bt75/bt75.zmk.yml

@@ -1,5 +1,5 @@
 file_format: "1"
-id: bt75
+id: bt75//zmk
 name: BT75 V1
 type: board
 arch: arm