refactor: replace filename hyphens with underscores

Aligns *.h and *.c to underscore naming convention.

These were kept (with warnings) for backwards compatibility with external boards/shields:
- kscan-mock.h
- matrix-transform.h
They should be removed in the future.

PR: #523

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

@@ -4,11 +4,6 @@
  * SPDX-License-Identifier: MIT
  */
 
-#pragma once
+#warning "kscan-mock.h has been deprecated and superseded by kscan_mock.h"
 
-#define ZMK_MOCK_IS_PRESS(v) ((v & (0x01 << 31)) != 0)
-#define ZMK_MOCK_PRESS(row, col, msec) (row + (col << 8) + (msec << 16) + (0x01 << 31))
-#define ZMK_MOCK_RELEASE(row, col, msec) (row + (col << 8) + (msec << 16))
-#define ZMK_MOCK_ROW(v) (v & 0xFF)
-#define ZMK_MOCK_COL(v) ((v >> 8) & 0xFF)
-#define ZMK_MOCK_MSEC(v) ((v & ~(0x01 << 31)) >> 16)
+#include "kscan_mock.h"

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

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#define ZMK_MOCK_IS_PRESS(v) ((v & (0x01 << 31)) != 0)
+#define ZMK_MOCK_PRESS(row, col, msec) (row + (col << 8) + (msec << 16) + (0x01 << 31))
+#define ZMK_MOCK_RELEASE(row, col, msec) (row + (col << 8) + (msec << 16))
+#define ZMK_MOCK_ROW(v) (v & 0xFF)
+#define ZMK_MOCK_COL(v) ((v >> 8) & 0xFF)
+#define ZMK_MOCK_MSEC(v) ((v & ~(0x01 << 31)) >> 16)

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

@@ -4,7 +4,6 @@
  * SPDX-License-Identifier: MIT
  */
 
-#define KT_ROW(item) (item >> 8)
-#define KT_COL(item) (item & 0xFF)
+#warning "matrix-transform.h has been deprecated and superseded by matrix_transform.h"
 
-#define RC(row, col) (((row) << 8) + (col))
+#include "matrix_transform.h"

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

@@ -0,0 +1,10 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define KT_ROW(item) (item >> 8)
+#define KT_COL(item) (item & 0xFF)
+
+#define RC(row, col) (((row) << 8) + (col))