Add missing licensing header

Fixes #205

app/include/dt-bindings/zmk/keys.h

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
 
 #pragma once
 

app/include/dt-bindings/zmk/kscan-mock.h

@@ -1,3 +1,9 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
 #pragma once
 
 #define ZMK_MOCK_IS_PRESS(v) ((v & (0x01 << 31)) != 0)

app/include/dt-bindings/zmk/matrix-transform.h

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
 
 #define KT_ROW(item) (item >> 8)
 #define KT_COL(item) (item & 0xFF)

app/include/dt-bindings/zmk/rgb.h

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
 
 #define RGB_TOG 0
 #define RGB_HUI 1

app/include/zmk/split/bluetooth/service.h

@@ -1,3 +1,9 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
 #pragma once
 
 int zmk_split_bt_position_pressed(u8_t position);

app/include/zmk/split/bluetooth/uuid.h

@@ -1,3 +1,9 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
 #pragma once
 
 #include <bluetooth/uuid.h>